We present the infrared spectroscopy study of three types of human healthy and cancerous tissues using standard ATR and fiber optics based ATR techniques. The use of fiber based ATR probes eliminates the need to bring the sample under the study to the spectroscopic instrument and opens the path for the application of infrared spectroscopy for the studies in situ and in vivo. The study revealed that conventional portable FTIR spectrometers with room temperature DTGS detectors cannot be readily used when coupled with fiber probes due to the high loses of the optical signal, but this problem can be overcome by combining an additional more sensitive liquid nitrogen cooled MCT detector to the system. The potential of the system is demonstrated in the cases of the studies of three types of tumorous tissues: kidney, bladder and brain. The studies of the tissue smears and untreated (wet) tissues indicated that “water free” fingerprint region has clear spectral signatures for the tumor identification. Depending on the tissue, the signatures are based on the glycogen infrared absorption bands for kidney tissue and the collagen absorption bands for bladder tissue. Brain tissue examination also shows some promising spectral markers for which precise establishment the higher data sets are still needed.