There is considerable evidence for an association between pathological gambling and scores on validated psychometric measures of erroneous gambling-related cognitions. However, a potential problem with this literature is that samples of pathological gamblers score higher on indicators of co-morbidity (e.g. substance misuse) that are also associated with poorer decision-making and reasoning abilities. We aimed to examine the relationship between pathological gambling and gambling-related erroneous beliefs after controlling for alcohol misuse. A sample of 140 regular gamblers completed a detailed psychological assessment including measures of pathological gambling (NORC DSM-IV Screen Self-Administered), delusion proneness (the Peters et al. Delusions Inventory), alcohol use (the Alcohol Use Disorders Identification Test) and gambling beliefs (Gambling-Related Cognitions Scale). Pathological gamblers scored higher than other regular gamblers on all these measures. Although alcohol use disorder was not directly related to delusion proneness, a combination of higher alcohol use disorder and delusion proneness was associated with higher gambling-related cognition scores. Our findings confirm previous evidence supporting an association between pathological gambling and greater endorsement of erroneous gambling-related cognitions. Alcohol misuse and delusion proneness may be factors that strengthen this association.