OBJECTIVES: The aim of the present study was to determine the characteristics and short-term outcomes of mother-infant pairs with comorbid drug dependency and psychiatric disorders. METHODS: A population-based retrospective chart review was carried out of 879 drug-dependent mother and infant pairs in New South Wales (NSW) and the Australian Capital Territory (ACT) who delivered between 1 January and 31 December 2004. RESULTS: Psychiatric comorbidity (dual diagnosis, DD) was identified in 396 (45%) of the 879 drug-dependent women. DSM-IV depression (79%), followed by anxiety (20%), was most prevalent. DD women were more likely to use amphetamines (29% vs 18%, p < 0.05), less likely to use opiates (42% vs 51%, p < 0.05) and to have had no antenatal care (24% vs 8%, p < 0.05). They also had more previous pregnancies (4, range = 2-5 vs 3, range = 2-5, p < 0.05) and domestic violence (29% vs 14%, p < 0.05) was more common. DD infants were less likely to be admitted to a nursery (47% vs 55%, p < 0.05). Withdrawal scores were similar (maximum median Finnegan scores = 4 (interquartile range = 3-8) vs 10 (interquartile range = 7-12, p = 0.30) but fewer needed withdrawal medication (19% vs 27%, p < 0.05). Maternal psychotropic agents did not worsen the severity of neonatal withdrawal. CONCLUSIONS: Psychiatric comorbidity, especially depression, is common and affects almost half of drug-using mothers. Antenatal care, drug use and social outcomes are worse for DD mothers and their infants. It is recommended that all drug-using women be assessed antenatally for psychosocial disorders so that timely mental health intervention can be offered, if required.