A theoretical study of the vibrational structure of the (X) over tilde(2)A＇ pound and (B) over tilde(2)A＇ excited states of the formyl radical, HCO, and its deuterated form, DCO, has been performed. The potential energy surfaces have been computed by means of a multiconfigurational perturbative method, CASPT2. The computed geometries and the harmonic and anharmonic frequencies are successfully compared to the available experimental information. The vibrational intensities of the transition (B) over tilde(2)A＇<->(X) over tilde(2)A＇ have been computed both for absorption and emission. The results lead to accurate determinations of several structural parameters and some reassignments of the vibrational transitions of the so-called hydrocarbon flame bands of the formyl radical.