Abstract: The invention concerns adducts of 1,8-dihydroxy-9-anthrone, of formula: ##STR1## in which: R.sub.1 and R.sub.2, taken together, form one of the following divalent residues: ##STR2## R.sub.3, R.sub.4, R'.sub.4, R.sub.5 and R'.sub.5 representing H, an alkyl group having 1-8 C with the exception of R.sub.5 =R'.sub.5 =CH.sub.3, a monohydroxyalkyl group with 2-8 C, possibly interrupted by one or more oxygens, a cycloalkyl group having 4-6 C, a phenyl group, or a benzyl group.Utilization of the compounds (I) in human or veterinary medicine, in particular in the treatment of psoriasis and or warts, and in cosmetics.