  We model light curves of flares observed in blazars, assuming that they are
produced by relativistic electrons/positrons injected by forward-reverse shocks
traveling down the jet with relativistic speeds. We approximate the radiating
region as a thin shell enclosed between the two shock fronts. In addition to
the conventional radiation processes such as synchrotron radiation and its
Comptonization, we take into account Comptonization of light originating in the
broad emission line region, and Comptonization of IR radiation from hot dust.
We demonstrate that flares produced in the adiabatic regime decay much slower
than flares produced in the radiative regime. The lack of such a difference
between the X-ray and $\gamma$-ray flares in 3C279 strongly supports the
synchrotron-self Compton (SSC) mechanism as responsible for X-ray production in
this object. Finally, we discuss a possible scenario which can explain the
`cooling' nature of the MeV peak in blazars by comparing the flares produced in
soft $\gamma$-ray band and above 100 MeV.
