  We investigate the c-axis optical conductivity and d.c. resistivity of
cuprate superconductors in the normal state. Assuming that the interlayer
hopping is incoherent we express the conductivity with planar spectral
functions obtained (i) from angle-resolved photoemission experiments, (ii)
using marginal Fermi liquid ansatz, and (iii) with the finite-temperature
Lanczos method for finite two-dimensional systems described by the t-J model.
Here in the low doping regime a pseudo-gap opening in the density of states
appears to be responsible for a semimetallic-like behavior of the D.C.
resistivity. In the optimally doped regime we find an anomalous relaxation
rate. Analytically this result is reproduced with the use of the marginal Fermi
liquid ansatz for the self energy with parameters obtained from the exact
diagonalization results.
