The present invention relates to heat and storage stable vinyl polymer polyol secondary dispersions containing A) at least one vinyl polymer resin having functional groups selected from hydroxyl, carboxyl and/or sulfonic acid groups and dispersed in a water/solvent mixture in the presence of a neutralizing agent, and B) at least one amphiphilic polymer built up from a hydrophobic and a hydrophilic segment. The invention also relates to a process for the preparation of the vinyl polymer polyol secondary dispersions by preparing vinyl polymer resin A) by polymerizing a mixture of ethylenically unsaturated monomers a) in the presence of an initiator b) in a water/solvent mixture and adding at least one amphiphilic polymer B), then at least partly neutralizing and dispersing the resulting product, optionally after the addition of a further amount of water.