On the reality of compact groups of galaxies

The problem of the reality of Compact Groups of galaxies (CGs) is discus se d. We separated two classes of groups: elongated, chain-like groups (I), an d round ones (II). The number of chain-like groups among Hickson Compact Gr oups (HCGs) is about twice as large as that of the round ones. In Shakhbazi an Compact galaxy Groups (ShCGs) the proportion of chain-like groups is sma ller than that of the round ones. It is shown that some parameters of both classes of HCGs are quite different. The radial velocity dispersion (sigma( nu)) is smaller in chain-like groups, and the interaction and merging proce sses are more efficient in them. The magnitude difference between the brigh test and the second brightest galaxies in HCGs is larger in groups of class I, and is smaller in groups with larger number of members. The surface dis tribution in round CGs is concentrated towards the center. The above-mentioned differences allow us to conclude that CGs are real phys ical entities.