Objectives: To identify young adults' stated reasons for not taking asthma medication and to determine the significance of personality, asthma control and health-related quality of life in relation to these stated reasons. Background: Reasons for non-adherence to asthma medication treatment have previously been studied, but research on the significance of personality in relation to stated reasons for not taking asthma medication is limited. Methods: Young adults with asthma (age 22years; n=216) stated their most common reasons for not taking asthma medication and completed postal questionnaires on personality, asthma control and health-related quality of life (HRQL). Results: The most common reason for non-adherence was ". No perceived need" (n=141). Participants giving this reason for not taking asthma medication scored lower on the personality trait Negative Affectivity and reported both higher asthma control and higher mental HRQL. "Insufficient routines" was the second most common reason (n=66), and participants stating it scored higher on Negative Affectivity and reported lower asthma control. An increase in asthma control increased the odds of stating ". No perceived need" as the reason for not taking asthma medication. An increase in Negative Affectivity was associated with an increase in the odds of giving ". Insufficient routines" as a reason. Conclusions: The personality trait Negative Affectivity and perceived asthma control played a role in the young adults' stated reasons for not taking asthma medication, which indicates that these parameters are of importance to young adults' medication management. © 2013 Elsevier Inc.