Integral and differential distributions of sunspot diameters are studied for last seven 11-year cycles of solar activity. Some data of the Greenwich catalogue, of Pulkovo’s data base and of bulletin “Solniechnyie Dannyie” are used. It is found that the average index of integral distribution α is 6.0 for the diameter range from 50 to 90Mm and does not dependfrom Wolf’s number. However, for the majority ofcycles (fourfrom seven) the average index of integral distribution depends on cycle’s phase: it is maximum for the grown phase, intermediate for the peak of α cycle and minimum for the phase of recession. Cycles 17,18, and 22 have an alternative evolution of а index. For these cases the value of a index does not depend on a phase of the cycle or the evolution of a index differs from one described above. It is revealed that cycles 17 and 18 are peculiar by sunspot diameters, namely, during these cycles the largestsunspots up to 140-180Mm were observed. Three assumptions in relation to the nature of these gigantic sunspots are proposed: a) these sunspots oc cur due to changes of differ en tial ro ta tion of the Sun; b) these sunspots are a separate unique statistical assembly which occurs sporadically in a discrete region of convective zone; c) these sunspots are ‘fragments’ of the relict magneticfield of the solar nucleus which come to the surface.