The attempt to forget some recently encoded information renders this information difficult to recall in a subsequent memory test. "Forget" instructions are only effective when followed by learning of new material. In the present study, we asked whether the new material needs to match the format of the to-be-forgotten information for forgetting effects to emerge. Participants studied visually presented words or line drawings (L1) and afterward were instructed to remember or forget these items. Then a 2nd conceptually unrelated list (L2) was presented that either matched or mismatched the format of L1. Forgetting effects were observed only when the lists matched in format but not when the formats mismatched. This result establishes an important boundary condition of directed forgetting and suggests that when salient retrieval cues guide retrieval, they eliminate the effect of the "forget" cue. Implications for theories of directed forgetting are discussed.