The aim was to examine barriers to initiation and continuation of treatment among individuals with common mental disorders in the US general population. Respondents in the National Comorbidity Survey Replication with common 12-month DSM-IV mood, anxiety, substance, impulse control and childhood disorders were asked about perceived need for treatment, structural barriers and attitudinal/evaluative barriers to initiation and continuation of treatment. Low perceived need was reported by 44.8% of respondents with a disorder who did not seek treatment. Desire to handle the problem on one's own was the most common reason among respondents with perceived need both for not seeking treatment (72.6%) and for dropping out of treatment (42.2%). Attitudinal/evaluative factors were much more important than structural barriers both to initiating (97.4% v. 22.2%) and to continuing (81.9% v. 31.8%) of treatment. Reasons for not seeking treatment varied with illness severity. Low perceived need was a more common reason for not seeking treatment among individuals with mild (57.0%) than moderate (39.3%) or severe (25.9%) disorders, whereas structural and attitudinal/evaluative barriers were more common among respondents with more severe conditions. Low perceived need and attitudinal/evaluative barriers are the major barriers to treatment seeking and staying in treatment among individuals with common mental disorders. Efforts to increase treatment seeking and reduce treatment drop-out need to take these barriers into consideration as well as to recognize that barriers differ as a function of sociodemographic and clinical characteristics.