  We review results about protoplanetary disk models, protoplanet migration and
formation of giant planets with migrating cores. We first model the
protoplanetary nebula as an \alpha-accretion disk and present steady state
calculations for different values of \alpha and gas accretion rate through the
disk. We then review the current theories of protoplanet migration in the
context of these models, focusing on the gaseous disk-protoplanet tidal
interaction. According to these theories, the migration timescale may be
shorter than the planetary formation timescale. Therefore we investigate planet
formation in the context of a migrating core, considering both the growth of
the core and the build-up of the envelope in the course of the migration.
