We offer a detailed treatment of minimal, maximal, dissipative, accumulative, self‐adjoint operator realizations with exit from space of boundary–value problem for Sturm‐Liouville equation with unbounded operator coefficient having discrete spectrum andwith boundary condition dependent on Herglotz‐Nevanlinna function of eigenparameter. We also study self‐adjoint operator realizations having purely discrete spectrum or having continuous spectrum which coincide with any interval on real axis. That is done in terms of boundary conditions. In addition, in particular case we obtain asymptotics of spectrum of self‐adjoint operators with discrete spectrum.