In most cases, addiction and mental conditions occur side by side. It is always a challenge to make the most accurate diagnosis in such cases because symptoms for the conditions usually overlap. An accurate diagnosis is only made when the overlapping symptoms are identified and attributed to one or more of the condition (Substance Abuse and Mental Health Services Administration, 2005). In such cases, more than one assessment tool is usually required to make an accurate assessment. In this study, the case of Marifel will be used to demonstrate the challenge of making accurate diagnosis for co-occurring conditions. The study will recommend the best assessment tool for addiction assessment/screening and assessment of the risk of harm. An accurate diagnosis will be made based on DSM-5 criteria. Finally, the study will address the strengths of the client, the challenges likely to be faced, and recommend the level of care based on ASAM criteria.