In this paper the reaction of allene with carbon dioxide is discussed, using [RhCl(C 2 H 4 )(P i Pr 3 )] 2 as catalyst. An unprecedented formal '2+2' allene-CO 2 reaction to afford a four-membered lactone is described. The influence of the temperature and pressure on the reaction of allene and CO 2 is highlighted. The role of addition of hydrogen to the reaction system, as modulator of the products distribution is discussed. The behavior of the catalyst [RhCl(C 2 H 4 )(P i Pr 3 )] 2 towards H 2 is also described and the structure of the resulting Rh hydride species inferred through a theoretical study.