One of the challenges faced by modern medicine is finding new methods of functional imaging of biological tissues in patients that allow detection of early tumor response to treatment. One of such methods proposed in this work is multimodal optical coherence tomography (MM OCT). It combines cross-polarization OCT (CP OCT) for visualization of tissue structure and assessment of connective tissue health, OCT-based microangiography (OCT MA) for visualization of the vasculature, and OCT- based elastography for measuring tissue stiffness. The efficacy of this method was tested during the course of photodynamic therapy (PDT), as major PDT targets are cellular and vascular components of a tumor. The experiments were carried out on the CT26 colon carcinoma transplanted into the mouse ear. It was shown that the efficacy of PDT can be assessed using MM OCT. For example, CP OCT can help differentiate between necrotic and intact tumors; OCT MA detects blood circulation defects that lead to slower blood circulation or circulatory stagnation followed by tumor death. OCT-based elastography is helpful in assessing stiffness of normal and pathological tissues.