The proposed study involves developing and evaluating an interactive, web-based CBT intervention for OEF/OIF Veterans with hazardous or problematic substance use and PTSD symptoms (PTSD or subsyndromal PTSD). The intervention will address the special culture and experiences of the investigators targeted population (OEF/OIF Veterans). The web-based CBT intervention includes 24 modules, to be used across 24 sessions targeting OEF/OIF Veterans with hazardous or problematic substance use and PTSD symptoms. The investigators ask participants to complete 2 sessions per week (one module per session) for 12 weeks. The first 18 modules to be completed across 18 sessions (9 weeks) are considered core modules relevant to all Veterans in the target population. These modules are designed to reduce posttraumatic stress symptoms as well as reduce and prevent the escalation of problematic substance use. The remaining 6 module topics are considered "optional" and are used based on the interest and clinical need of various sub-groups of VA patients. The study includes initial input as well as feedback on a beta version from experts who have worked with OEF/OIF veterans with PTSD and substance abuse problems as well as input/feedback from the target population (the Veterans themselves). In addition to presenting content grounded in evidence-based CBT interventions, the program also employs state of the art technologies to deliver module content grounded in evidence-based learning principles, including Computer-Assisted Instruction, Computer Simulation and other interactive exercises.