In visual backward masking, a target is followed by a blank screen (ISI - Inter-stimulus-interval) and, then, a mask which deteriorates target processing. Schizophrenic patients show strong but complex processing deficits in visual masking compared to healthy controls. Recent genetic, behavioral, and clinical studies suggest that functional psychoses (schizophrenia, bipolar disorder, schizoaffective disorder), previously thought to be distinct from each other, belong to one continuum. The shine-through masking paradigm has been proven to be a reliable endophenotype of schizophrenia with a high sensitivity and specificity discriminating between patients, their clinically unaffected relatives, and healthy controls. Here, we examined whether the complex masking effects, we found in schizophrenia patients previously, are also found in other psychotic and non-psychotic patients, namely, depressive patients and abstinent alcoholics. We tested 28 schizophrenic, 22 schizoaffective, 20 bipolar patients, 26 major depressive patients, 23 abstinent alcoholics, and 24 healthy control subjects with various variants of the shine-through masking paradigm. All 3 groups of psychotic patients showed a very similar pattern of masking deficits. Masking was strongly prolonged compared to controls: Schizophrenia patients needed ISIs of 110 ms, bipolar patients of 125ms, schizoaffective patients of 130 ms and controls of only 30ms. These prolonged ISIs were not caused by deteriorated spatial or temporal resolution as two additional experiments show. Interestingly, patients with unipolar major depression and abstinent alcoholics performed like healthy controls. We suggest that patients with functional psychoses suffer from similar visual dysfunctions whereas visual processing of depressive patients is different.