In the thermal neutron–induced fission of 233U, the cumulative and independent yields of various fission products within the mass ranges of 77 to 109 and 123 to 155 have been measured by using an off-line gamma-ray spectrometric technique. The lower yields of 86Br and 136I than usual trend indicate the formation of delayed neutron emitters 87Br and 137I. From the cumulative yields, the post-neutron mass yield distribution was obtained after applying the charge distribution correction. The data from the present and earlier work of our laboratory in the 233U(nth,f) reaction were compared with similar data of 232,235U(nth,f) and 238U(n,f) reactions to examine the effect of mass difference of the fissioning systems on the fine structure of the mass yield distribution. The mass yield distribution in the 233U(nth,f) reaction was also compared with those of 229Th(nth,f), 241Pu(nth,f), and 245Cm(nth,f) reactions to examine the effect of charge and mass difference of the fissioning systems and also to examine the different behaviors of standard I and standard II asymmetric modes of fission.