For prediction of the effectiveness of laser-induced thermotherapy (LITT) of liver metastases and for the planning of laser treatment it is indispensable to achieve knowledge about the intrahepatic light and temperature distribution in order to obtain data for an optimally adapted dosimetry. We evaluated the optical properties of normal and tumorous rabbit-liver ex-vivo using a double integrating sphere technique as well as a Monte-Carlo- simulation. These data were correlated with the measurement of the intrahepatic temperature distribution in-vivo during LITT. In our study we were able to show a positive correlation between ex-vivo results of optical properties and in-vivo results in temperature distribution. The absorption coefficient and scattering coefficients were significantly smaller in tumor tissue than in normal liver. This resulted in a higher optical penetration depth of the laser light into the tumor tissue (p < 0.01). Temperature measurement near the applicator was lower in tumor tissue, than that distant from the applicator (p < 0.01) corresponding to a higher temperature penetration depth. Both, higher optical and thermal penetration depth in the tumorous tissue was correlated with a significant increase in coagulation volume after LITT.