  We study the neutrino oscillation problem in the framework of the wave packet
formalism. The neutrino state is described by a packet located initially in a
region S (source) and detected in another region D at a distance R from S. We
examine how the oscillation probability as a function of variable R can be
derived from he oscillation probability as a function of time t, the latter
being found by using the Schrodinger equation. We justify the known
prescription "t --> R/c" without referring to a specific form of the neutrino
wave packet and only assuming the finiteness of its support. The effect of the
oscillation damping at large R is revealed. For an illustration, an explicit
expression for the damping factor is obtained using Gaussian packet.
