X-ray diffraction and volumetric studies of two liquid crystalline alkenyl derivatives reveal a pronounced influence of the alkenylation and the position of its double carbon-carbon bond on the molecular packing of these compounds. 1-(4'-Cyanocyclohexyl)-trans-4-(1-penten-5-yl)-cyclohexane and 1-(4'-cyanocyclohexyl)-trans-4-(2-penten-5-yl)-cyclohexane show lower levels of the molecular overlap in the formation of their dimers in the nematic phase and higher molecular packing than the corresponding 1-(4'-cyanocyclohexyl)-trans-4-n-pentylcyclohexane.