Our secondary aims are to test the same hypotheses based on 3-month (end of treatment) sustained abstinence and 7-day point prevalence at 1, 3, and 6 months with biochemical verification at 3 and 6 months. Exploratory aims will study the Tweet2Quit groups' social network structures with a focus on the identification of buddy pairs and social brokers and test if these relationships are stronger for women in women-only groups versus women in coed groups of Tweet2Quit.