  In this exploratory study, two photon decay widths of pseudo-scalar
($\eta_c$) and scalar ($\chi_{c0}$) charmonium are computed using two ensembles
of $N_f=2$ twisted mass lattice QCD gauge configurations. The simulation is
performed two lattice ensembles with lattice spacings $a=0.067$ fm with size
$32^3\times{64}$ and $a=0.085$ fm with size $24^3\times{48}$, respectively. The
results for the decay widths for the two charmonia are obtained which are in
the right ballpark however smaller than the experimental ones. Possible reasons
for these discrepancies are discussed.
