An explicitly exact superconformal description is provided to some classes of type II string theories in non constant RR backgrounds. This is done by applying the manifest (2,2) approach of Berkovits and Maldacena to type II strings and by studying the condition of exact conformal invariance of certain supersymmetric backgrounds. We find a new set of exact type-IIA strings with non constant RR 2-form and 4-form curvatures and for type IIB with non constant 3-form curvature.
