  We consider hidden charm pentaquarks as hadroquarkonium states in a QCD
inspired approach. Pentaquarks arise naturally as bound states of quarkonia
excitations and ordinary baryons. The LHCb $P_c(4450)$ pentaquark is
interpreted as a $\psi'$-nucleon bound state with spin-parity $J^P=3/2^-$. The
partial decay width $\Gamma(P_c(4450)\to J/\psi+N)\approx 11$ MeV is calculated
and turned out to be in agreement with the experimental data for $P_c(4450)$.
The $P_c(4450)$ pentaquark is predicted to be a member of one of the two almost
degenerate hidden-charm baryon octets with spin-parities $J^{P}=1/2^-,3/2^-$.
The masses and decay widths of the octet pentaquarks are calculated. The widths
are small and comparable with the width of the $P_c(4450)$ pentaquark, and the
masses of the octet pentaquarks satisfy the Gell-Mann-Okubo relation.
Interpretation of pentaquarks as loosely bound $\Sigma_c\bar D^*$ and
$\Sigma_c^*\bar D^*$ deuteronlike states is also considered. We determine
quantum numbers of these bound states and calculate their masses in the
one-pion exchange scenario. The hadroquarkonium and molecular approaches to
exotic hadrons are compared and the relative advantages and drawbacks of each
approach are discussed.
