We demonstrate that IR spectroscopic analysis can be used in diagnosis and chemotherapy monitoring for cancers of various organs at the molecular level. We used Fourier transform IR spectroscopy to study human breast and thyroid tumor tissues which were removed during surgery. The characteristic frequencies of C = O stretching vibrations in the IR spectra of tissues of pathological foci were compared with data from histological examination. In the IR spectra of healthy tissues or for benign tumors, the most intense absorption bands ν(C = O) are located in the interval 1675–1650 cm^–1. When malignant neoplasms are present in the organs, the intensity of the bands in this range of the spectrum is reduced, while the intensities of the absorption bands in the 1710–1680 cm^–1 interval increase. We also studied lung tissue for mice of the C₅₇B1/6 line for healthy tissue and after implantation of B-16 melanoma tumor. The IR spectra of healthy mouse lung tissue and mouse lung tissue with B-16 melanoma metastases in the region of the C = O stretching vibrations display the same differences. We found that when lung malignancy was treated with the optimal dose of a synthesized drug based on palladium complexes of methylenediphosphonic acid, the spectroscopic signs of the presence of metastases in the lungs disappear, and the IR spectrum of the lung tissue after treatment practically coincides with the spectrum of healthy lung tissue.