In this study, the effect of the selective phosphodiesterase type 4 (PDE4) inhibitor rolipram on memory performance was investigated using the object recognition task. First, three doses of rolipram (0.01, 0.03 or 0.1mg/kg) were tested with a 24h delay between the learning (T1) and the test (T2) trial. Doses of rolipram were injected at different time points (30min before T1, immediately after T1 or 3h after T1). In a second experiment, the effects of rolipram (0.03, 0.1 or 0.3mg/kg) were tested in combination with scopolamine (0.1mg/kg) applying a 1h delay between trials. Both substances were administered 30min before T1. Using a 24h interval, rolipram showed an improvement in long-term memory performance when injected 3h after T1 at a dose of 0.03mg/kg. Further, rolipram reversed the scopolamine-induced short-term memory deficit at a dose of 0.1mg/kg. Although the improved memory performance in both conditions is likely to be explained by elevated cAMP levels, two separate working mechanisms might explain these effects.