We analyse the properties of the partitioned densities of states in mesosco
pic transport problems. In terms of an imaginary-potential model, a concise
derivation of the local partial density of states (LPDOS) is given. Using
a numerical method to calculate the functional derivative of the scattering
matrix, a detailed study of different kinds of decomposed densities of sta
tes in double-barrier structures is carried out. We find that the dynamical
local density of states dn(alpha alpha) (x)/dE and the global partial dens
ity of states (GPDOS) dN(alpha alpha)/dE in the nonclassical regime cannot
be neglected in full quantum calculations.