  The global structure of optically thin hot accretion disks with radial
advection included has been investigated. We solve the full energy conservation
equation explicitly and construct the radial structure of the disk. It is found
that advection is a real cooling process and that there are two solutions
co-exist for a given mass accretion rate less than a critical limit. One is
fully advection cooling dominated and the other is dominated by local radiative
cooling. The advection dominated accretion disks are hotter than the local
cooling dominated disks; they are most probably in the two-temperature regime
and effects such as electron-positron pair production and annihilation may need
to be considered to study the microphysics of the hot plasma. However, the
global disk structure will not be much affected by the local radiative process.
