The identification of patients carrying an increased risk of psychosis is one of the most important demands in schizophrenia research. Currently used diagnostic instruments mainly focus on either attenuated psychotic symptoms and brief limited intermittent psychotic symptoms or solely cognitive basic symptoms. The "Early Recognition Inventory based on IRAOS" (ERIraos) has been developed as a comprehensive assessment of both symptom groups within one scale. We compared the results obtained by ERIraos with an international standard instrument, the "Comprehensive Assessment of At Risk Mental States" (CAARMS) and applied both scales in a sample of 121 outpatients positively tested on a screening checklist for at risk mental states (ARMS). Subsamples were classified as first episode of psychosis, late ARMS with prevalent attenuated psychotic symptoms and/or brief limited intermittent psychotic symptoms, earlier stages of ARMS presenting cognitive basic symptoms as well as a vulnerability group, also differing regarding mean age and psychosocial functioning. Our results point to a higher sensitivity of ERIraos compared to scales that mainly focus on attenuated psychotic symptoms and brief limited intermittent psychotic symptoms. A detailed assessment of cognitive basic symptoms seems to be important in early detection, might be an important focus for therapeutic interventions in ARMS patients and might sustain attempts to alleviate cognitive dysfunction in schizophrenia.