The aim of the present study was to analyse whether the Portuguese version of the Postpartum Depression Screening Scale (PDSS) was a valid instrument for screening postpartum depression. For this purpose the following objectives were delineated: (1) to analyse PDSS psychometric properties; (2) to determine PDSS cut-off points and associated conditional probabilities for screening depression according to DSM-IV and ICD-10 criteria; and (3) to compare the performance of PDSS with the Beck Depression Inventory-II (BDI-II) in screening for postpartum depression. Four hundred eighty-six 3-months-postpartum women completed both questionnaires and were interviewed with the Portuguese version of Diagnostic Interview for Genetic Studies (DIGS). The Portuguese version of the operational criteria checklist for psychotic illness (OPCRIT) was used to obtain DSM-IV and ICD-10 diagnoses of depression, our gold standards for caseness. PDSS reliability and validity were very good and equivalent to those reported in other versions, including the original. PDSS was an accurate screening instrument for postpartum depression, showing satisfactory combination of sensitivity and specificity (>80%). Compared to BDI-II it has the advantage of being more specific for the motherhood context. PDSS could be very useful for clinical and epidemiological purposes.