  Time evolution of the expectation values of various dynamical operators of
the harmonic oscillator with dissipation is analitically obtained within the
framework of the Lindblad theory for open quantum systems. We deduce the
density matrix of the damped harmonic oscillator from the solution of the
Fokker-Planck equation for the coherent state representation, obtained from the
master equation for the density operator. The Fokker-Planck equation for the
Wigner distribution function, subject to either the Gaussian type or the
$\delta$-function type of initial conditions, is also solved by using the
Wang-Uhlenbeck method. The obtained Wigner functions are two-dimensional
Gaussians with different widths.
