Abstract: The present invention relates to a resin solution composition for paints or adhesives which comprises an acid-modified butene-1/&agr;-olefin copolymer obtained by modifying a butene-1/&agr;-olefin copolymer with an unsaturated carboxylic acid or an acid anhydride thereof. The butene-1/&agr;-olefin copolymer comprises, as polymerizable components, 65 to 85 mol % butene-1 component and 15 to 35 mol % &agr;-olefin component having 2 to 8 carbon atoms other than butene-1 component. The acid-modified butene-1/&agr;-olefin copolymer comprises the unsaturated carboxylic acid or the anhydride thereof in a proportion of 0.5 to 5% by weight. In this resin solution composition, the acid-modified butene-1/&agr;-olefin copolymer is dissolved in an organic solvent, in a solid content of 10 to 30% by weight.