The present invention relates to a reactor for the photocatalytic treatment of liquid or gas currents, comprising a pipe which the current to be treated flows through. At least one light source, at least one planar means M1 and at least one planar means M2 are arranged inside said pipe, wherein M1 has at least one photocatalytically active material and M2 reflects the light radiation emitted from the at least one light source. The reflective surface of the at least one means M2 and the inner wall of the pipe together form an angle that is greater than or equal to 0°, such that the light emitted from the light source is reflected from the at least one means M2 onto the photocatalytically active material. The invention further relates to a method for the photocatalytic treatment of liquid or gas currents by irradiation of light in the reactor according to the invention.
