The influence of temperature changes on the thermal and structural behaviour of crystalline solvates of tetraphenylporphyrin (H2TPP) with 1,4-dioxane and of tetraphenylporphyrin copper complexes (CuTPP) with benzene were investigated using thermogravimetry, differential scanning calorimetry and X-ray powder diffraction. Simultaneous application of thermal and structural techniques made it possible to observe the complex evolution of the desolvation processes. These techniques enabled : (a) the separation of the two crystalline phases appearing during the process, (b) the detection of changes of the symmetry of the crystal lattice of CuTPP crystalline solvate from monoclinic and triclinic, (c) the determination of the heat and activation energy of desolvation process, and (d) the observation of reversible thermal effects for H2TPP.