Fluorescence spectra and quantum yield of graphitic (g-C3N4) and spherical (s-C3N4) modifications of carbon nitride were measured. It was found that the intensity of the fluorescence at the maximum is more than two orders as high for carbon nitride spheres as for graphitic carbon nitride particles. The high value of the fluorescence quantum yield (QY), up to 32% at excitation 532 nm and 38% at excitation 633 nm, was attributed to the spherical shape of this form of carbon nitride. One of the interesting features of the fluorescence excited in s-C3N4 is the high intensity of the anti-Stokes fluorescence.