Season 1
The first season deals with Addison's move from Seattle to Los Angeles and her attempts to adjust to a very different type of working environment at Oceanside Wellness Group, a co-op private practice. The first season also deals with her budding relationships with her new co-workers. Among them include her best friend Naomi Bennett, a fertility specialist, and her ex-husband Sam Bennett, who specializes in internal medicine. Also working within the practice is psychiatrist Violet Turner, pediatrician Cooper Freedman, alternative medicine specialist Pete Wilder, and receptionist Dell Parker. It is revealed early on that the Bennetts established the practice with the rest of the doctors owning a share of it as well. Charlotte King, who serves as chief of staff at St. Ambrose Hospital, works with Oceanside Wellness through her dealings with Sam and her sexual relationship with Cooper
Season 2
The first half of the second season dealt with the practice's financial troubles. Naomi reveals to Addison that they are in danger of losing the practice due to unpaid debt causing Addison to tell Sam. This in turn causes a shift within the practice making Addison the new boss. Adding to the drama was the competition of a new practice, Pacific Wellcare. This new practice, located within the same building as Oceanside Wellness, was run by Charlotte causing turmoil for her and Cooper. Another happening within this season is the dynamic between Sam and Naomi who by the finale realize they can no longer be friends as well as the deepening romantic relationship of Cooper and Charlotte. Addison was romantically linked with Kevin Nelson (played by David Sutcliffe), a police officer, but later realized their relationship was going nowhere. Towards the end of the season, Addison falls in love with cardiovascular surgeon Noah Barnes, who as it turns out, is married and is expecting his first child. Matters become more complicated when Addison realizes that Noah's wife is one of her patients. Archer Montgomery (Grant Show), Addison's playboy brother, also made sporadic appearances causing trouble for her and Naomi. Archer was found to be with an aggressive brain tumor which was later diagnosed as parasites. Addison sought the professional help of her ex-husband, Derek Shepherd (Patrick Dempsey). After Derek successfully saved Archer, Addison discovered he was back to his old tricks cheating on Naomi.
Season 3
In the third season, Violet survives from the cliffhanger from season two thanks to Pete, Naomi and Addison. She gives Pete their baby, Lucas, while she recovers from the ordeal. Addison and Sam get even closer and develop feelings for each other, but decide not to become a couple because they don't want to hurt Naomi. Charlotte and Cooper break up, and Dell loses Heather in an explosion which nearly kills Betsey also.
Addison and Pete become a couple, which causes Addison to get close to Lucas until Violet wants him back, even going as far as taking Pete to court to get joint custody. Sheldon starts to fall for Charlotte after they start to sleep together and Sam and Naomi's daughter, Maya, gets pregnant and marries the father of her baby, Dink.
Addison and Pete become a couple, which causes Addison to get close to Lucas until Violet wants him back, even going as far as taking Pete to court to get joint custody. Sheldon starts to fall for Charlotte after they start to sleep together and Sam and Naomi's daughter, Maya, gets pregnant and marries the father of her baby, Dink.
Season 4
Addison and Sam continue their relationship and all seems to be well until Addison's mother, Bizzy, commits suicide forcing Addison to re-evaluate her life. She loves Sam but is currently broken up by the fact that she wants children but he doesn't. Normally Addison would talk to her best friend Naomi but their friendship is not the same anymore so she feels all alone. With no one to turn to her biggest challenge is to find someone she can be completely open with.