Postnatal depression in mothers is commonplace as it affects 10–15% of recent mothers. Postnatal depression is still an under-diagnosed illness and if unidentified, is often left untreated. If left untreated, the depression can have an adverse effect not only on the mother, but also on the child's development and on the well-being of the whole family. The aim of this survey was to investigate the prevalence of postnatal depressive symptoms among Finnish mothers and to ascertain the relationship with sociodemographic factors in mothers. A sample of 1000 families at 2 months postnatal was studied by mailing the Edinburgh Postnatal Depression Scale to mothers and a questionnaire on demographic characteristics to mothers and fathers. The response rate was 39%. The data were examined by means of frequency and percentage distributions. Connections were examined using Spearman correlation coefficient and analysis of variance. In all, 373 mothers and 314 fathers took part in the study. Fifty-five (13%) mothers had depressive symptoms. Results show that the number of pregnancies, deliveries or children, the mode of delivery or the mother's age were not associated with depressive symptoms. However, mothers who had depressive symptoms had fewer years of education, shorter duration of breast-feeding and were more dissatisfied with family life compared with mothers who exhibited no depressive symptomatology. The families of mothers with depressive symptoms had also experienced more problems and changes having a profound impact on the family compared with other mothers.