We used highly luminescent CdSe/CdS/CdZnS (core/shell/shell) colloidal quantum dots (QDs) prepared by a standard chemical synthesis method dispersed in low concentration into toluen in a 1 mm length quartz cuvette. The two-shell structure of QDs provides an effective retention of wave functions of electrons and holes inside QDs, as well as a high photochemical stability. The inner shell between the core and the outer shell allows one to reduce mechanical stresses inside the QD, since CdS has a lattice parameter intermediate between CdSe and CdZnS, which allows obtaining a significant PL quantum yield of these QDs (up to 85%).  A sample with the photoluminescense (PL) peak at 628 nm was studied by transmission electron microscopy, optical absorption spectroscopy, and luminescence spectroscopy. It was determined that the diameter of the CdSe nucleus of QD amounts to 5.4 nm with the size dispersion of 8%. The thickness of the CdS/CdZnS shell was 2.6 nm. The PL in QDs was excited by a single 30 ps pulse of the second harmonic (539 nm) of a mode-locked YAlO3:Nd3+ laser at room temperature. The spectral decomposition of the PL signal collected from the front face of the cuvette was performed using a polychromator. The PL kinetics was recorded by a streak camera. The PL spectrum is located along the streak camera entrance slit. The image of time-resolved PL spectrum of QDs obtained on the streak camera screen was registered by a digital camera. The spectral resolution was about 5 meV and 9 meV for the time-integrated mode and the time-resolved mode, respectively, and an overall time resolution of about 40 ps was obtained. The time-resolved kinetics of PL is presented in Fig. 1. The observed dependence of the PL intensity on the time is represented by circles. A thin solid line corresponds to the analytical solution of the coupled rate equations explained in the text. Thick lines describe PL kinetics from excitons (solid) and biexcitons (dotted) separately. The exciting pulse of duration 38 ps is centered at time 154 ps. Insert: Transient PL spectrum recorded at t=208 ps, integrated in 50 ps gate (circles) and its fitting curve (thin solid line). PL spectra for excitons (thick solid line) and biexcitons (thick dashed line). Normalized time-integrated PL spectrum is shown as shaded area.  To describe the results of our measurements and find the decay times of the exciton and biexciton components of radiation, we propose simple theoretical models that take into account the effects of filling the states of single excitons and biexcitons. We determine the spectral positions and widths of the exciton and biexciton bands of photoluminescence and the biexciton binding energy.