  The AMS-02 experiment confirms the excess of positrons in cosmic rays (CRs)
for energy above 10 GeV with respect to the secondary production of positrons
in the interstellar medium. This is interpreted as evidence of the existence of
a primary source of these particles. Possible candidates are dark matter or
astrophysical sources. In this work we discuss the possible contribution due to
pulsars and their nebulae. Our key assumption is that the primary spectrum of
electrons and positrons at the source is the same of the well known photon
spectrum observed from gamma-rays telescopes. Using a diffusion model in the
Galaxy we propagate the source spectra up to the Solar System. We compare our
results with the recent experiments and with the LIS model
