The impact of severe spatial confinement on the phase transition behavior of smectic liquid crystals has been systematically studied. Dodecylcyanobiphenyl (12CB) and octylcyanobiphenyl (8CB) liquid crystals were confined to controlled-pore glasses of various pore radii R. The phase transition behavior was studied by means of high-resolution ac calorimetry. The results show that the carbon tails length of the liquid crystal molecules strongly influences the phase behavior. In 8CB samples strong pretransitional effects were observed; however, these effects were substantially weaker in 12CB samples. Moreover, a crossover between first and second order phase transition character was observed in 12CB samples upon decreasing R. The observed behavior is explained in terms of surface-memory effects and a dimensional crossover. (C) 2012 Elsevier B.V. All rights reserved.