The ability to detect cancer at its earliest stages, called “dysplasia”, is the key of its successful treatment. Optical techniques, such as diffuse reflectance and intrinsic fluorescence, may improve the ability to detect gastrointestinal (GI) dysplasia since they have the potential to provide morphological and biochemical information of normal and malignant tissues. However, those optical tissue properties can only be provided if it is possible to extract information from the measured diffuse reflectance and intrinsic fluorescence signals. This paper presents the implementation and the validation of a preliminary Monte Carlo based inverse model to extract optical tissue properties, such as the absorption and the scattering coefficients, from diffuse reflectance experimental measurements in phantoms. ; This work is funded by FEDER funds through the "Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, project reference COMPETE: FCOMP-01-0124-FEDER-020241, and by FCT- Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010. S. Pimenta thanks the FCT for the SFRH/BD/87605/2012 PhD grant.