Abstract Three crystal structures of N-methylacetamide (NMA) with the xanthenol host 9-(4-methoxyphenyl)-9H-xanthen-9-ol (H) are reported. The crystal structures were obtained by using different solvent compositions. The host compound was dissolved in equimolar mixtures of N-methylacetamide/N,N-dimethylacetamide, N-methylacetamide/1,4-dioxane and N-methylacetamide/aniline which yielded H·NMA, H·2NMA and 2H·2NMA, respectively; H·NMA and 2H·2NMA are polymorphs. Thus, compounds with 1:1 and 1:2 host:guest ratios were obtained. H·NMA solved in the monoclinic space group P2₁/n whereas both H·2NMA and 2H·2NMA were solved in the triclinic space group P 1 ¯ . $P\bar 1.$ For all structures each host molecule is hydrogen bonded to one NMA molecule via (Host)-OH···O-(NMA) linkages. The NMA guests occupy channels and are connected via N–H···O hydrogen bonds forming chains. The thermal stabilities of the compounds were determined using thermogravimetry and differential scanning calorimetry which indicated that 2H·2NMA was the least stable with H·2NMA being the most stable.