Background and objective: Propofol may decrease seizure duration in electroconvulsive therapy. Although not proven, prolonged seizures may be more efficacious. The goal of this study was to evaluate and compare effects of alfentanil and remifentanil on seizure duration, recovery parameters and degree of stimulus amplitude in patients undergoing electroconvulsive therapy. Methods: Twenty-four ASA I–II patients enrolled in this prospective, randomized trial, each receiving a total of seven electroconvulsive therapies. Patients were randomized to receive only Propofol, group P (0.75 mg kg−1, n = 8), Propofol with alfentanil, group A (10 µg kg−1 alfentanil + 0.5 mg kg−1 Propofol, n = 8) and Propofol with remifentanil, group R (1 µg kg−1 remifentanil +0.5 mg kg−1 propofol, n = 8) via an iv route. Supplemental doses of propofol were given as required to achieve loss of consciousness. Succinylcholine 0.5 mg kg−1 iv was given to all groups for muscular paralysis. We recorded hemodynamic parameters, cortical and motor seizure durations, and recovery parameters. Results: Mean motor seizure duration was found to be significantly longer in patients receiving propofol-remifentanil anesthesia (53.3 ± 13.6 s) and propofol-alfentanil anesthesia (52.2 ± 0.4 s) compared with propofol anesthesia (37.6 ± 9.2 s) (P = 0.001). Recovery parameters and stimulus amplitudes were similar in groups A and R; significantly different from group P (P = 0.001). Conclusions: Adding 10 µg kg−1 alfentanil or 1 µg kg−1 remifentanil to reduced doses of propofol provided unconsciousness and increased seizure durations. For patients who need higher stimulus amplitudes for longer seizure durations, combining low-dose propofol with alfentanil or remifentanil may be good alternative regimens for ECT.