Objective: Individuals with posttraumatic stress disorder (PTSD) show a high risk of developing substance use disorders (SUD). Many studies have shown that PTSD often precedes SUD, and some studies have been able to identify factors that might predict which individuals might develop subsequent SUD. Attempts to treat PTSD and SUD comorbidity have proven difficult, but new methods for simultaneous treatment have shown promise for treating PTSD. The ability to identify factors that predict PTSD/SUD comorbidity and the advent of new combined treatment methods warrant investigation of how differences in specific types of PTSD symptoms individuals experience might predict who will go on to develop SUD symptoms and thus benefit from new combined treatments. Method: In this study, we analyzed which clusters of PTSD symptoms predicted whether individuals with PTSD met criteria for alcohol use disorder. Results: Analyses revealed that frequency and intensity of negative alterations in cognition and mood predicted SUD, but re-experiencing symptoms, hyperarousal, and avoidance did not. Conclusions: Our results indicate that those who experience negative alterations in cognition and mood may be at increased risk of developing SUD, and that we may be able to predict which individuals in clinical settings will be strong candidates for new combined PTSD/SUD treatments. Further considerations for our results and for future directions are also discussed.