Purpose Neurocognitive outcomes are frequently used as indicators of real-world functioning in schizophrenia spectrum disorders (SSD). These test results may be influenced by individual differences, such as affective dispositions. Here we investigate the relationship between positive and negative affect and neuropsychological test scores in a large, mixed-gender, population based group of participants without co-morbid substance abuse. Materials and methods We assessed 129 male and female SSD patients with the Positive and Negative Affect Schedule (PANAS) and a comprehensive neuropsychological test battery. Results and conclusions The neuropsychological test scores were mainly predicted by age and gender, with small contributions from negative psychosis symptoms. There was a statistically significant relationship between Positive Affect and processing speed and between Negative Affect and verbal memory and executive function. However, the level of neurocognitive function variance explained by these affects was only 5%. Thus, the neurocognitive test results were not associated with trait affect in any clinically significant manner. This adds to previous findings of no relationship between affective dispositions and psychosis symptom variables in our participants. We suggest that affective traits constitute an independent dimension that may influence well-being, coping, and real-life outcome in SSD patients directly, and not through neurocognitive function.