  We study the pseudoscalar, vector and axial current correlation functions in
SU(2)-NJL model with scalar and vector couplings. The correlation functions are
evaluated in leading order in number of colors $N_c$. As it is expected in the
pseudoscalar channel pions appear as Goldstone bosons, and after fixing the
cutoff to reproduce the physical pion decay constant, we obtain well-known
current-algebra results. For the vector and axial channels we use essentially
that at spacelike momenta the correlation functions can be related to the
experimentally known spectral density via dispersion relations. We show that
the latter imposes strong bounds on the strength of the vector coupling in the
model. We find that the commonly used on-shell treatment of the vector and
axial mesons (identified as poles at large timelike momenta) fails to reproduce
the behavior of the corresponding correlation functions at small spacelike
momenta extracted from the physical spectral density. The parameters of the NJL
model fixed by the correlation functions at small spacelike momenta differ
noticeably from those of the on-shell treatment.
