Clark and Lana had to overcome numerous obstacles to be together, the first of which was Lana's long term relationship with Whitney Fordman. Although Whitney left Smallville after a year, Lana was still conflicted by her loyalty to Whitney and her growing feelings for Clark. When she discovered that Whitney was dead, she embraced her feelings for Clark, although there were underlying problems in their relationship due to Clark's secrets and strange behavior when he was exposed to red kryptonite. Realizing that she could not trust Clark, Lana eventually decided to leave Smallville to study in Paris.
Attempting to escape her relationship with Clark, Lana tried to create a new life for herself in Paris, where she met Jason Teague and quickly started a relationship with him. Nevertheless, she was drawn back to Smallville when the Mark of Transference appeared on her back, which she recognized from the Kawatche Caves.
As she returned, it wasn't long before Lana met up with Clark again. Lana had already confided in Lois Lane about Jason and shortly afterwards Lois let slip to Clark about Lana's "hot summer fling", which surprised and disappointed him. Jason soon followed Lana to Smallville in order to continue their relationship, much to Lana's delight.
Jason quickly established himself in the community by taking a job at Lana's school as the High School Football Assistant Coach. In this role, Jason had to start a working relationship with Clark when he requested to join the football team. Jason seemed to get on well with Clark, as he remained protective of Clark when the rest of the football team took a dislike to him. He also seemed to have faith in Clark to make a good impression with a Metropolis University scout.
Unaware that Jason was the one that Lana had been seeing during the summer, Clark nearly caught the pair of them kissing. Despite being frustrated by the lies that Clark told her during their relationship, Lana was now forced to lie to Clark to conceal her relationship with Jason and protect his job. Lana was keen to avoid the mistakes that she had made with her relationship with Clark and tried to maintain an honest relationship with Jason so took him to the Kawatche Caves to show him the similarity between her new magical tatoo and the cave painting.
Clark thought there was still hope for him and Lana when he saw her watching his first football game. Lana claimed to be there for him, although she was actually there for Jason. Lana confided in Jason that she had never been happier in their relationship. However, when Jason drank the Ceerleaders love potion, he became jealous of Clark and Lana’s obvious ongoing feelings for one another and attacked Clark in his loft warning him away from his girlfriend. After the potion wore off, Jason apologized to Clark and Clark understood that Jason wasn't himself and insisted that there were no hard feelings. Nevertheless, Clark remained curious as to who Jason's girlfriend was and, when asked, Jason claimed not to know.
Clark eventually discovered their relationship after he switched bodies with Lionel Luthor. Lana and Jason were kissing in his office when Lionel-as-Clark walked in on them. Surprised to see the two of them together, he rudely criticised their relationship, shocking Jason and angering Lana. Not realizing that this was in fact Lionel, when Clark switched back to his own body, Lana confronted Clark about what he saw. She insisted that her relationship with Jason was serious and requested that Clark keep it secret. Lana was unaware that her attempt to keep this secret had actually just revealed the truth. Clark was shocked and disappointed that Lana was seeing Jason.
Clark confided in Lex Luthor about how difficult it was to see Lana with Jason, but insisted that he wanted Lana to be happy. Therefore, Clark maintained a friendly and professional relationship with Jason during the deciding game for the State championship. However, Jason became suspicious of Clark when he tripped an injured another player who outweighed him by 100 pounds. Realizing that getting on the wrong side of Clark could expose his relationship with Lana, Jason warned Clark that Coach Quigley suspected him of being on performance enhancing drugs and faked a clean test result. After telling Lana this, she ensured Jason that he didn't have to worry about her leaving him for Clark because she was committed to her new relationship.
Lex reported Jason's relationship with Lana and had him fired. Lana immediately suspected Clark, who was disappointed that she would think the worst of him. Despite the breakdown in his relationship with both Lana and Jason, Clark came to their rescue when Countess Margaret Isobel Thoreaux possessed Lana and risked Jason's life. This appeared to restore their trust in him, as Jason then returned the favor and rescued Clark after Isobel had depowered him and tied him up. After Lex told Lana that he was the one that had Jason fired, not Clark, Lana apologized to Clark and confided in him about the tatoo. Clark feigned ignorance to its meaning, which did not help their relationship.
Jason was clearly still uneasy about Lana and Clark's relationship as, when he became infected by a toxin that had leaked out from LuthorCorp, Jason hallucinated that Lana was cheating on him with Clark. As Jason's hallucination continued, he confronted Lana but Clark beat him up and Lana stabbed him. This coincided with Jason falling off the balcony at the Talon, as his hallucination effected his actions in real life.
Lana was extremely concerned about Jason as he lay in a coma at Smallville Medical Center in a panic state. Lana put her trust in Clark to help discover what had happened to Jason but, once he was cured, Jason broke up with Lana. Suspecting that this was because he wanted a sexual relationship, Lana tried to seduce him in order to win him back. Jason admitted that this was not the reason that he ended the relationship and confided in her that he suspected his mother had orchestrated their meeting. Lex discovered this to be true, as Jason was initially more interested in acquiring the Stones of Power than his relationship with Lana. However, as Jason repeatedly claimed that he did not like what he was turning into, he relied on his relationship with Lana to make him the man he wanted to be.
Meanwhile, Clark embarked on a new relationship with Alicia Baker. Despite her previous Kryptonite psychosis and attempt on Lana's life, Clark saw the good in her and believed that she had changed. Nevertheless, Lana continued to distrust Alicia and snubbed both her and Clark, which added more strain to her rocky relationship with Clark. Jason supported Lana with this and confronted Clark saying how disgusted he was with Clark's decision to trust someone like Alicia. Matters were made worse when there was another attempt on Lana's life by a mysterious assailant. Jason rescued Lana from almost being strangled. As this happened in a locked room, Alicia was the main suspect. Clark fiercely defended his new girlfriend but, when Jason was also nearly strangled and found with Alicia's scarf around his neck, Clark took Lana and Jason's side, doubting Alicia's innocence. However, he regretted this when Lois discovered Tim's feelings about Lana and Jason's immoral relationship and confessed to framing and then murdering Alicia.
As Clark's relationship with Alicia came to a tragic end, Lana's relationship with Jason also hit a rocky patch, when Lex revealed the truth about her supposed chance meeting with Jason in Paris. As Jason's search for the stones intensified, they became less honest with each other, with Jason secretly going to China and Lana hiding the Crystal of Air from him. Conversely, at the same time, Lana's trust in Clark increased, as she enlisted his help in searching for one of the stones in China. She also danced with Clark at their senior prom after she decided it was a bad idea to take Jason seeing as he was fired from there because of their relationship. Nevertheless, Jason went to the dance and saw how close Lana and Clark were. Clearly jealous, Jason angrily left.
Realizing the problems in their relationship, Lana suggested that she and Jason end their relationship. Jason immediately suspected that this was because of her feelings for Clark, which she denied. Nevertheless, he quickly became jealous and angry, which scared Lana and caused her to re-evaluate her feelings for Clark.
Lana was enthusiastic about reuniting with Clark when he got amnesia, as she felt they were able to leave their problems behind them. She made a date to go out with him that night despite leaving things up in the air with Jason. Nevertheless, by then Clark had recovered all of his memories except from the last 24 hours. Lana was disappointed by this and Clark was surprised at her openness to reigniting their relationship. At first, Clark seemed concerned about pursuing Lana behind Jason’s back, but Lana insisted that they had just made plans as friends. Clark remained unconvinced and, in order to prevent losing her again, insisted that if they reunite it would be different this time. Although Jason and Lana never had proper closure to their relationship, Lana grew closer to Clark, especially when they had the chance to bond more when they discovered baby Evan and took care of him.
Jason neglected his relationship with Lana, as he got closer to finding the stones. He resorted to kidnapping Lionel and Lex with his mother's help and tortured them to reveal the location of the stones. When Lionel revealed that Lana had one, Genevieve left to confront her. Lionel tried to convince Jason to turn on his mother by appealing to his feelings for Lana. Jason was torn between his desire for the stones and Lana's safety but the Luthors ultimately overpowered him before he could make his decision.
Jason tried to convince Lex not to kill him by attempting to explain Clark's involvement in all the mysterious events. Nevertheless, Lionel shot him and he fell off a cliff. This revealed that Jason knew about Clark's secret, although he had not exposed it, despite the tension between them due to their feelings for Lana. It was later revealed that the reason behind this was because of his family's association with Veritas, which had made a committment to protecting the Traveler.Jason's death was confirmed in the newspaper after the second meteor shower. As Lana read it, she expressed no remorse at the loss of her boyfriend, as she had become convinced that he had only pursued a relationship with her in order to help him find the stones. After this, Lana confronted her feelings for Clark and they reignited their relationship.
As their relationship quickly became serious, Clark confessed that he was still a virgin. Lana was surprised that he hadn't had sex with Alicia and admitted that she and Jason had also not slept together. Clark was pleased about this and then felt comfortable with starting a sexual relationship with her.