The effect of cation-pi interactions on some NMR data of ethylenic complexes has been investigated by B97-1, PBE1KCIS and MPWKCIS1K methods using 6-311++G(3df,3pd) basis set. Unlike 3J(H-H)((cis)), the chemical shift of ethylenic hydrogen (delta(H)) and 3J(H-H)((trans)) increases by cation-pi interaction. The changes of NMR data have been considered with regard to geometry and direct electronic effects. Also, the distance dependence of NMR parameters has been studied in these complexes. (C) 2010 Elsevier B.V. All rights reserved.