Forty-three depressed inpatients, referred for electroconvulsive therapy, and 30 manic patients were examined with clinical ratings and regional cerebral blood flow (rCBF) determinations. The depressed patients were mainly medication free, while most of the manic patients were medicated. Both patient groups showed a normal cerebral blood flow level and regional distribution compared with age- and sex-matched normal controls. In the depressed group and especially in the unipolar subgroup, a significant positive relationship was found between the mean rCBF and symptoms of depression and cognitive dysfunction. Eighteen of the depressed and 18 of the manic patients were reexamined in a euthymic state following treatment and recovery. Only minor and statistically nonsignificant flow changes were found in connection with the clinical improvement. In the manic patients, a significant negative relationship was found between neuroleptic dosage and rCBF.