The transformation from self-supporting lianas to host-supported climbing lianas is related to re-allocation of biomass and nutrients among plant organs. Therefore first variations in leaf mass per area (LMA) leaf carbon and nitrogen allocation and 13C and 15N natural abundances were analysed among three tropical Passiflora species (P. edulis P. ligularis and P. tripartita) in a greenhouse study. Second the influence of a climbing support was considered for each species and parameter. P. ligularis leaves were most enriched in 13C in both treatments when compared with the other two species. This enrichment was caused by a high LMA which is related to a high internal resistance to CO2 diffusion. For P. edulis and P. tripartita d13C was additionally increasing with nitrogen content per area. Generally there were no differences when considering carbon and nitrogen allocation to leaves of host-supported and self-supporting lianas. The only hints towards increased investment into leaves after the transition from self-supporting to host-supported stages could be seen by a trend to increased leaf areas and masses. d13C values of supported P. edulis or P. tripartita plants were significantly increasing faster than those of non-supported plants once the interactions of leaf mass or nitrogen content per area were accounted for. Hence the offer of a climbing support had only a minor impact on d13C or d15N values in vitro but this could be different with increasing age of lianas in vivo.