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The article concerns the possibility of precise picosecond lifetime measurements by the method of the time correlated single photon counting (TCSPC). The lifetimes (τ) of S2 fluorescence of xanthione measured in different solvents have shown that it is possible to obtain τ as short as a few picoseconds. The values of τ varying from ∼5 to ∼38 ps in solvents whose refraction indices range from 1.34 to 1.50 have been proposed as picosecond standards in lifetime measurements. However, in order to obtain reliable results some conditions must be met: the effect of the absorbing and emitting impurities must be eliminated, the instrument response function (IRF) must be very stable and correctly determined, and because of a much lower time resolution of the TCSPC method relative to that of the upconversion method, the procedure of measurements and numerical analysis of results proposed in our work should be applied. In the study reported the effect of impurities was eliminated by applying high performance liquid c...