In this paper we summarize results of several research projects devoted to development of new diagnostic methods and procedures based on quantitative infrared thermography in medical applications. First, basics of active dynamic thermography are presented. Described are both, instrumentation and software comprising measurement procedures including collection of series of IR-images after external excitation, data treatment with displacement corrections, reduction of noise and artifacts and finally presentation of parametric diagnostic images. The thermal tomography method is also shortly discussed. As the most important for medical diagnostics parametric images of thermal time constants are discussed. For illustration of the value of presented methods chosen research and clinical applications performed in several clinics of Gdansk Medical University are presented. In vivo experiments on animals, mainly domestic pig, as well as clinical diagnostic procedures are discussed in skin burn and cardiosurgery applications. Specific requirements of IR-thermal investigation in medical applications are discussed in comparison to IR-thermal imaging in technical non-destructive evaluation. It should be underlined that medical applications of IR-diagnostics seem to be the most difficult among other applications as heat transfers in living tissues are far more complicated comparing to technical