  We compare two different approaches used for calculating cross sections for
the two-photon $p p \to l^+ l^- X$ process. In one of the approaches photon is
treated as a collinear parton in the proton. In the second approach a recently
proposed $k_T$-factorization method is used. In this presentation we discuss
sensitivity of the results to the choice of structure function parametrization
and experimental cuts in the $k_T$-factorization approach. We compare results
of our calculations with recent experimental data for dilepton production and
find that in most cases the contribution of the photon-photon mechanism is
rather small. We discuss how to enhance the photon-photon contribution. We also
compare our results to those of recent measurements of exclusive and
semi-exclusive $e^+ e^-$ pair production with certain experimental data by the
CMS collaboration.
