Three polymers with pyrrolidone-containing side chains (NPES, NPHS, and NPDS) with different spacer lengths between the main chain and the pyrrolidone group were synthesized by the reaction of cross-linked poly[styrene-co-4-(chloromethyl)styrene] with 1-(2-hydroxyethyl)-, 1-(6-hydroxyhexyl)-, and 1-(12-hydroxydodecyl)pyrrolidones, respectively. Interaction of these polymers with phenols was investigated in terms of the effect of the length of the spacers. The interaction strength was estimated by the binding constant K obtained from Klotz plots in water and chloroform solutions. K values with phenol were greater in water (28.2 mo/L for NPES, 30.1 mol/L for NPHS, 35.5 mol/L for NPDS) and were larger than in chloroform (17.2, 22.8, and 22.3 mol/L, respectively). Hydrophobic interaction in water is suggested as an additional effect besides hydrogen bonding and charge-transfer interaction. The order of K values in water (NPDS > NPHS > NPES) may arise from differences in degree of freedom and hydrophobicity of the spacer. In chloroform, K values for NPHS and NPDS were similar but larger than those of NPES with all the phenols. Small differences in R between NPHS and NPDS might be explained by the steric hindrance effect of the spacer of NPDS. The dihydroxy compounds catechol and 2,3-dihydroxynaphthalene showed 4-10 times larger K values than phenol and beta-naphthol. There is a clear correlation between K and the acidity of the phenol.