A possible influence of comets on the growth of heavy elements abundance suggested several years ago by Tinsley and Cameron is shortly reviewed. Such an effect would be significant if the formation of comets produce cometary material equivalent to 0.01 - 0.02 M per one solar mass. In the view of current hypothesis of the formation and structure of cometary nuclei the role of comets should be considered as one of the possible moderators of the Z value variation during the chemical evolution of our Galaxy.