The size-dependent ac-conductivity of a small metallic particle is stu
died for electrons enclosed in a box with random impurities. The exact
wave functions and energies are calculated numerically up to 500 elec
trons, then the Kubo-formula is evaluated, and an ensemble average is
performed. A strong size- and frequency dependence of the conductivity
is found which is in good agreement with random matrix results. The s
ize dependence of the dc-conductivity agrees qualitatively with microw
ave absorption measurements on submicron particles.