The infrared and Raman spectra of liquid mixtures of HCONH2 and HCOND2 are presented. Contrary to what is expected, the isotropic Raman spectra of the mixtures show only one carbonyl stretching band, whose position depends upon the composition of the mixture. It is shown that the apparent collapsing of bands is not due to fast exchange between different "sites" (i.e. the fast exchange limit). Similar phenomena have been observed previously in solids. Thus, the phenomenon might reflect "solid-like" behavior of liquid formamide close to its melting point. The depolarized component of the Raman Spectrum and the IR spectrum of the carbonyl stretching band are observed at approximately the same frequencies, whereas the isotropic components are observed at a lower frequency (noncoincidence). The same is observed for the NH2 bending mode. The noncoincidence splitting of this mode is shown to follow a model for binary mixtures of isotopomers developed by Logan. The asymmetry of the IR and Raman bands can be explained in terms of two "sites", one belonging to a hydrogen-bonded species and the other to a "free" species without hydrogen bonding to the carbonyl group, but maybe forming hydrogen bonds to the carbonyl group of other formamide molecules.