Four series of liquid crystal dimers have been prepared containing either ether‐linked or methylene‐linked spacers. Changing the spacer from being ether‐linked, i.e. O(CH2) n O, to methylene‐linked, i.e. (CH2) n +2, results in decreased nematic–isotropic transition temperatures, and this reduction is more pronounced for odd‐membered spacers. By contrast, the entropy change associated with the nematic–isotropic transition is higher for an even‐membered methylene‐linked dimer than for the corresponding ether‐linked material. This trend is reversed for odd members. These observations are completely in accord with the predictions of a theoretical model developed by Luckhurst and co‐workers in which the only difference between the dimers is their shape. For the highly non‐linear pentamethylene‐linked dimers, only those with a short terminal chain exhibited fluid smectic behaviour, specifically, a monotropic alternating SmC structure which allowed for the efficient packing of the bent molecules. Once the terminal chain reached a value of m = 9, a modulated ordered smectic phase was observed. For even‐membered dimers, which exhibit only nematic phases upon melting for short terminal chain lengths, smectic phase behaviour was promoted with increasing terminal chain length, as is conventionally observed. Even‐membered ether‐linked dimers exhibited a SmC phase whereas even‐membered methylene‐linked dimers exhibited an ordered smectic G/J phase. Thus, it would appear that the differences in the transitional properties of ether‐ and methylene‐linked dimers can be accounted for largely in terms of geometrical factors.