While serious mental disorders typically show socioeconomic differences similar to physical illness-that is, that lower positions imply poorer health-differences for common mental disorders have been inconsistent. We aim to clarify the associations and pathways between measures of socioeconomic circumstances and common mental disorders by simultaneously analysing several past and present socioeconomic measures. The data were derived from middle-aged women and men employed by the City of Helsinki. Cross-sectional surveys were conducted in 2000-2002 among employees who, during each year, reached 40, 45, 50, 55 or 60 years of age. The pooled data include 8970 respondents (80% women; response rate 67%). Common mental disorders were measured by GHQ-12 and the SF-36 mental component summary. Seven socioeconomic measures were included: parental education, childhood economic difficulties, own education, occupational class, household income, home ownership, and current economic difficulties. Logistic regression analysis was used to examine associations between the socioeconomic circumstances and common mental disorders. Past and present economic difficulties were strongly associated with common mental disorders, whereas conventional past and present socioeconomic status measures showed weak or slightly reverse associations. Adjusting for age and gradually for each socioeconomic measure did not affect the main findings, which were very similar for women and men, as well as for both measures of common mental disorders. While the associations of conventional socioeconomic status measures with common mental disorders were weak and inconsistent, our results highlight the importance of past and present economic difficulties to these disorders.