Micro and nano structures of titanium dioxide (TiO 2 ) are well-known for their photocatalytic application. High surface area and high light scattering efficiency in such structures enhance their photocatalytic activity. The present work explores the possibility of enhancing photocatalytic activity through mesoporous TiO 2 spheres by exploiting the coexistence of high porosity and morphology dependent resonance (MDR) modes. A controlled synthesis of TiO 2 spheres with nano-crystalline grains of anatase phase and high surface area of about 96 m 2 /g has been successfully accomplished leading to mesoporous particles with uniformly distributed pores of small diameters much less than the wavelength of incident light. Despite the high porosity, MDR modes are observed in the photoluminescence spectrum of a single sphere. As inclusion of pores may produce significant changes in the refractive index (RI) of the resonator, and as the quality and density of the modes depend on the RI of the resonator, it is important to have a procedure to determine the RI of the resonator as well as to characterize the MDR modes. An iterative procedure that is quite general is presented for mode identification and for the determination of the porosity-induced reduction in the RI and for ascertaining the presence of chromatic dispersion. The presence of high surface area as well as of MDR modes of reasonably high Q-factor makes these particles promising for photo electrochemical applications. © 2018 Author(s).