  The purpose of this work is to spectroscopically analyse the classical
Cepheid V708 Car. A preliminary check of the spectrum of V708 Car showed that
this is a lithium-rich supergiant. We also found that V708 Car has an unusual
chemical composition in that the abundances of various elements correlate with
their condensation temperatures. We tried to find an explanation of this
feature, which is unusual for classical Cepheids. For the spectroscopic
analysis, we used methods based on the assumption of local and non-local
thermodynamic equilibrium. We determined the fundamental parameters of our
program star V708 Car. This long-period Cepheid has a mass of about 12
M$_{\odot}$. We derived the abundances of 27 chemical elements in this star.
They are clearly correlated with their condensation temperature: the higher the
condensation temperature, the lower the abundance (there are exceptions for
sodium and barium, however). We explain this peculiar chemical composition of
the V708 Car atmosphere by the gas-dust separation in the envelope of this
star. A similar mechanism leads to the observed peculiarities of the chemical
composition of $\lambda$ Boo, W Vir, and asymptotic giant branch stars.
