The study presents theoretical and empirical comparison of the three indexes in Rorschach Comprehensive System that were developed for psychotic functioning assessment: the Schizophrenia Index (SCZI), the Ego Impairment Index (EII) and the Perceptual Thinking Index (PTI). In spite of the conceptual and nominal differences, these indexes significantly overlap and includes common indicators. The study compared a discrimination value of these three indexes, as well as and theirs indicators and based on the obtained results, tried to formulate a new index as a composite of the best predictors.