In the present study, we examine whether higher rates of mental health service use observed among single-parent mothers is due to greater need (psychopathology) or other factors (predisposing and enabling characteristics) using a socio-behavioural model of health care use. We use data from two large surveys in Canada (the 1994-95 National Population Health Survey and the 1990 Ontario Mental Health Supplement). The bivariate results from both surveys revealed that single-parent mothers were two to three times more likely than married mothers to have sought professional help for mental health reasons over a 12-month period. Multivariate analyses showed that differences in predisposing and enabling characteristics between single and married mothers accounted for very little of the relationship between family structure and service use. Rather, differences in the prevalence of psychiatric disorders accounted for the higher use of services among single mothers. Single mothers are more likely than married mothers to seek professional help for mental health concerns. The use of services appears equitable in that need (higher rates of psychopathology) is the major factor differentiating use between married and single mothers. Further work should examine differences in pathways into formal care between single and married mothers.