Picosecond time-correlated single photon counting system and time-resolved luminescence spectrometer were constructed, employing a mode-locked picosecond laser, fast electronics, and microchannel plate tube. It has been shown that the instrument response function critically depends on laser pulse shape, timing jitter and walk of the electronics, and characteristics of detector and amplifier. Correcting time dispersion in the optical system, the best instrument response function obtained appears to be 25 ps, which made it possible to measure the luminescence lifetime with less than 10 ps resolution in the picosecond to microsecond range. range.