Curable organopolysiloxane composition exhibiting improved adhesion in the cured form

Organopolysiloxane compositions curable by a hydrosilylation reaction contain a novel adhesion promoter consisting essentially of 1) a carboxylic acid ester containing an acryloyloxy or methacryloyloxy group and an alcoholic functional group and 2) an organosilicon compound containing a silicon-bonded vinyloxy or substituted vinyloxy group. The compositions exhibit excellent adhesion to both organic and inorganic substrates that are in contact with the compositions during curing. The adhesion on plastics is especially good.