The lysine residues of histone proteins can be acetylated or methylated, with important effects on gene expression. Until recently the protein modules that bind acetyl-lysine have been limited to bromodomains. However, the tandem plant homeodomain (PHD) finger of human DPF3b — which is involved in gene activation — has also been reported to bind to acetylated histones. Here, three-dimensional solution structures of DPF3b offer mechanistic insight into how this protein recognizes acetylation marks.