  The effect of narrow dibaryon resonances to nuclear matter and structure of
neutron stars is investigated in the mean-field theory (MFT) and in the
relativistic Hartree approximation (RHA). The existence of massive neutron
stars imposes constraints to the coupling constants of the omega- and
sigma-mesons with dibaryons. We conclude that the experimental candidates to
dibaryons d1(1920) and d'(2060) if exist form in nuclear matter a Bose
condensate stable against compression. This proves stability of the ground
state for nuclear matter with a Bose condensate of the light dibaryons.
