The method of determination of the optical parameters of a cloud is applied to aircraft spectral radiation measurements in cloud layers and the spectral dependencies of the scattering and absorption coefficients are calculated for four experiments. A strong spectral dependence of the scattering coefficient and a high value of the absorption coefficient are obtained. The explanation of these facts and empirical formulas for obtaining true values of optical parameters of clouds are proposed. The obtained values of true absorption can explain the so–called "anomalous short–wave absorption" by clouds.