A new two-phase swirl-flow monolithic-type reactor was designed to study the kinetics of heterogeneous photocatalytic processes on immobilized semiconductor catalysts. True kinetic rate constants for destruction of a textile dye were measured as a function of wavelength of light intensity and angle of incidence, catalyst layer thickness, and the effect of absorption of light by liquid film on the overall rate of photocatalytic degradation. Photocatalytic-activities of two commercially available TiO2 catalysts (Degussa P25 and Hombikat UV 100) were also compared for different light intensities and catalyst layer thickness. Residence time distribution and mass-transfer limitations were evaluated. This new reactor appears to be an attractive choice for kinetic studies of heterogeneous photocatalysis.