  We investigate the ground-state heavy quarkonium $\chi_{c1}(1P)$ and its
first excited state $\chi_{c1}(2P)$ with quantum numbers $J^{PC}=1^{++}$. The
masses and decay constants of these charmonium states are computed using
two-point QCD sum rule method by including quark, gluon and mixed condensates
up to dimension-8. We compare our numerical results with the available
experimental data as well as existing theoretical predictions in the
literature.
