Microcrystallites and ultra-thin films of BiI3 embedded in CdI2 crystals were prepared by the melt-growth method and the hot wall technique. Absorption spectra and Stokes-shifted photoluminescence bands of the excitons confined in those are presented. The Stokes-shifts and the temporal behavior of the luminescence bands are understood by considering the size-dependent exciton-lattice interaction and the size-dependent radiative decay rate. These results are compared with model calculations.