In the current study, semi-permeable alginate-oligochitosan microcapsules for multicellular tumor spheroids (MTS) generation were elaborated and tested, to estimate a response of the microencapsulated MTS (MMTS) to photodynamic therapy (PDT). The microcapsules (mean diameter 600 μm) with entrapped human breast adenocarcinoma MCF-7 cells were obtained using an electrostatic bead generator, and MMTS were generated by in vitro long-term cell cultivation. The formed MMTS were incubated in Chlorin e6 photosensitizer solution and then irradiated using 650-nm laser light. The cell viability was measured by MTT-assay in 24 h after irradiation, and histological analysis was performed. The proposed MTS-based model was found to be more resistant to the PDT than the two-dimensional monolayer cell culture model. Thus, MMTS could be considered as a promising three-dimesional in vitro model to estimate the doses of drugs or parameters for PDT in vitro before carrying out preclinical tests. Copyright © 2011 Wiley Periodicals, Inc.