The purpose of this study was to assess robustness of volumetric measurement of malignant pleural mesothelioma (MPM) before and after chemotherapy to modified RECIST. Thirty patients with digitally available chest CT scan before and after 3 cycles of chemotherapy were included. Three readers assessed independently tumour response using two different methods: Modified RECIST criteria and tumour volumetric approach using dedicated software (Myrian, Intrasense, France). Inter-rater reliability of uni-dimensional and volumetric measurements was assessed using intraclass correlation. tumour response classification for modified RECIST was compared to volumetric approach applying uni-dimensional RECIST volumetric equivalent criteria. The determination of uni-dimensional tumour measurement (RECIST) revealed a low inter-rater reliability (0.55) and a low interobserver agreement for tumour response classification (general kappa 0.33). Only 14 patients were classified equally. A high inter-rater reliability (0.99) and interobserver agreement (general kappa 0.9)) was found for absolute tumour volumes (volumetric measurements). 27 cases were classified equally. The number of cases classified as "stable disease" was higher for volumetric approach using tumour equivalent criteria compared to modified RECIST. Volumetric measurement of MPM on CT-scan using Myrian software is a reliable, reproducible and sensitive method to measure tumour volume and hence therapy response after induction chemotherapy.