Text in English / Against the background of high prevalence of substance abuse in the globe generally and South Africa in particular, research has shown an association between substance abuse and other mental disorders or vice-versa. With most rehabilitation centres offering separate diagnosis and treatment for the two disorders, the problem of relapse has been significant. The purpose of this study is to explore the perceived effectiveness of CBT as a treatment model for substance use disorders with co-occurring disorders. Subsequently, the research will add to the already existing research evidence. The study was conducted in five rehabilitation centres in Gauteng Province. The qualitative descriptive research approach was used to conduct the study. Both purposive and snowball sampling were used to recruit participants in this study. The sample consisted of CBT specialist participants from diverse race, gender, ethnicity, and age ranging from 30 to 65 years, with at least a minimum of five years’ experience. A pilot study with two specialist participants was conducted, and this enhanced trustworthiness and authenticity of the study. The primary method of qualitative data collection employed in this study was semi-structured individual interviews for specialist participants. Grounded theory analysis was employed to analyse data. The findings of the study emphasised a need to not separate treatment of substance use disorders and psychiatric pathologies. More importantly, the effectiveness of CBT in treating both disorders was established by the study. The study further encourages more time in therapy as the way to increase effective results accompanied by less relapse rate. Accordingly, the findings of this study encourage more research and use of CBT treatment for substance use disorders with co-occurring disorders in South Africa. This study found that the most used substances are both legal and illegal, and they are further classified as depressants, stimulants, opioids, and new psychoactive substances. A vulnerable population to abuse substances includes adolescent and young adults, individuals with co-occurring disorders, and low socio-economic status. The disorders that normally co-exist with substance use disorder ranges from depression, bipolar disorder, schizophrenia, sleeping disorder, impulsivity, antisocial behaviour, borderline disorder, paranoia, panic disorder, and suicide behaviour. The study found that genetic predisposition, depression, parental neglect and financial problems, experimentation with substances for relaxation, peer group pressure, and co-occurring disorders are high risk causes for substance abuse. The experience of participants in treating substance use disorder with co-occurring disorders involves which disorders get treated first, and the mental state of patients for effective treatment. The various substance abuse treatment models includes person centred approach, bio-psychosocial approach, holistic approach, eclectic therapy, integrated approach, resilient approach, rational emotive behavioural therapy, family therapy, motivational interviewing, 12-step programme, and cognitive behavioural therapy. The participants’ experience with CBT entails its usability in both individual and group therapy, the use of CBT skills after therapy, and CBT effectiveness in relapse prevention. Accessibility and affordability of CBT treatment is influenced by access to rehabilitation centres and cost of rehabilitation centres. Lastly, individual factors, family factors, and environmental factors are part of the contributing factors towards high relapse rates. / Psychology / M.A. (Psychology)