We extend the work of Herr A., Gardner R. and Walker J.M. (“An Experimental Study of Time-Independent and Time-Dependent Externalities in the Commons” in Games and Economic Behaviour, 19, p. 77-96), by studying an N-person discrete-time deterministic dynamic game of T periods fixed duration. The objective function is stage-additive and depends on a state variable, whose dynamic evolution is linked to past decisions of all players. The baseline treatment consists of a time dependent situation. The players have to decide whether to use a private good or, by paying a lump-sum fee, to extract on one of two imperfectly substitute Common-Pool Resources. Two kinds of externalities are considered (i) within period externality; and (ii) across period externality. In a first treatment, we consider only across period externalities. In a second treatment, both types of externalities are considered. The observations are confronted to three benchmark outcomes corresponding to distinct behavioural assumptions: (a) sub-game perfection, (b) joint payoff maximization, and (c) myopic behaviour.