We discuss the consistency conditions of a novel orientifold projection oftype IIB string theory on C^2/Z_N singularities, in which one mods out by thecombined action of world-sheet parity and a geometric operation which exchangesthe two complex planes. The field theory on the world-volume of D5-brane probesdefines a family of six-dimensional RG fixed points, which had been previouslyconstructed using type IIA configurations of NS-branes and D6-branes in thepresence of O6-planes. Both constructions are related by a T-dualitytransforming the set of NS-branes into the C^2/Z_N singularity. We alsoconstruct additional models, where both the standard and the novel orientifoldprojections are imposed. They have an interesting relation with orientifolds ofD_K singularities, and provide the T-duals of certain type IIA configurationscontaining both O6- and O8-planes.