The electronic conditions and direct optical transitions in a semiconductor quantized spherical film under 'strong' quantization regime are considered when the size of the system is smaller than that of a bulk exciton. A physically adequate model is suggested that allows to find analytically the energy spectrum and wave functions of the charge carriers in the layer. In an approximation of simple non-degenerate bands, the absorption coefficient for interband and 'intersubband'-inband transitions is found. Along with the frequency dependence, the explicit dependence of the absorption coefficient on the geometrical size of the model is revealed. (C) 2003 Elsevier B.V. All rights reserved.