Novel 11 C-radiolabelling method was applied for the investigation of methanol conversion on iron oxide modified mesoporous MCM-41. Changes in the selectivity were observed varying the state of the loaded iron species or the degree of the surface coverage with 11 C-radiolabelling methanol. Combining the Moessbauer spectroscopy, X-ray diffraction (XRD), N 2 -physisorption, and temperature-programmed reduction- thermogravimetric (TPR-TG) techniques with the high sensitive 11 C-radioisotopic catalytic analysis, the contribution of the different reaction pathways of methanol conversion was discussed.