The invention relates to addition compounds which are obtainable by reacting a) one or more polyisocyanates containing uretdione groups with b) one or more compounds of the formula (I) Y—(XH)n  (I) with the proviso that at least 50% of the free isocyanate groups of component a) are reacted with the compounds of the formula (I) to give an intermediate which contains uretdione groups, and subsequently the intermediate is reacted with c) one or more compounds of the general formula (II) Z—NHRm  (II) with the proviso that all free NCO groups optionally still present and at least 20% of uretdione groups originally used are reacted with Z—(NHR)m. The invention further relates to the use of the addition compounds as dispersants and dispersion stabilizers, and to a process for preparing them.