  The models developed to describe the spectral energy distribution (SED) of
blazars can be divided into leptonic or hadronic scenarios, according to the
particles responsible for the high-energy component. We have developed a new
stationary code which computes all the relevant leptonic and hadronic
processes, permitting the study of both leptonic and hadronic scenarios in a
consistent way. Interestingly, mixed lepto-hadronic scenarios (in which both
components contribute to the high energy emission) naturally arise in this
framework. We present the first application to the well known BL Lac object PKS
2155-304.
