Giant fluctuations of the intensities of local optical fields in fract
al clusters are established, dependent on a high Q factor (low dissipa
tion) of an optical resonance. We have shown that the nonlinear-optica
l enhancement by fractals is due to these fluctuations and not to a hi
gh mean magnitude of the local field. We have calculated the distribut
ion function P(G) of a relative local-field intensity G and found a ne
w scaling dependence, P(G) is-proportional-to G(-epsilon), with the in
dex epsilon independent of an excitation frequency and dissipation rat
e.