We analyze here measurement data on spectral dependence of the aerosol extinction coefficient within 0.44–12 μm spectral range, aerosol scattering coefficient at 0.52 μm wavelength, particle size distribution function within 0.4–10 μm, and mass concentration of soot in aerosol during a smoke haze observed in the West Siberia in October 1997. It is shown that the smoke haze results in an increase (by an order of magnitude or more) in the aerosol extinction and scattering coefficients in the visible range, as well as in the particle number density and soot content. Main changes of the parameters take place in the small-size aerosol fraction (sizes less than 1 μm) and, to a lesser degree, in the coarse aerosol fraction. It was found that the smoke haze smooths the peculiarities in the diurnal variation of the scattering coefficient and soot content characterizing the atmosphere free of smoke. Low relative content of soot in the smoke aerosol (1–4%) is indicative of a pyrolysis origin of the smoke haze particles formed during forest and peat fires. The smoke haze is assumed to contribute significantly to the planetary radiation budget.