A library of ethylene analogs of the previously described arylpiperazines with N-acylated amino acids was synthesized on SynPhase Lanterns and the library representatives were evaluated for their 5-HT(1A) and 5-HT(2A) receptor affinities. The obtained results were compared with those reported for compounds containing propylene and a butylene spacer and they revealed that 5-HT(1A) receptor affinity decreased proportionally with the length of the alkyl chain. Furthermore, the synthesized 3-cycloalkyl derivatives containing two methylene group spacers showed that the 3-position of pyrrolidine-2,5-dione preferred substituents of hydrophobic character.