Many industrial accidents in the recent past showed that the thermal decomposition of Cumene Hydroperoxide (CHP) can lead to runaway reactions and subsequent fires and explosions. Still this organic peroxide is extensively used in the petrochemical industry. This paper is aimed at a better understanding of the possible consequences of CHP decomposition by analyzing its thermal behavior when dissolved in a high boiling point solvent using two different adiabatic calorimeters. The experimental data obtained allowed us to assess the general trends on the main runaway parameters and to characterized the thermal decomposition of the mixture with respect to the peroxide concentration, as well as the influence of the thermal inertia of the equipment. The gas generation rate for each of experiment was calculated and then corrected to adiabatic conditions. The data generated can assist as a guidance for designing processes where CHP is involved, along with their safeguards.