Substance use disorder (SUD) is characterized by alcohol and drug use, dependence features and adverse psychosocial consequences. SUD represents an interplay between substance use, personality, impulsivity and psychopathology. Network analysis is a powerful method to examine the direct and indirect relationship between various variables, and could understand SUD as a self-sustaining system. We examined the network structure of addictive behaviour, personality, impulsivity and psychopathology in treatment-seeking people with SUD. This cross-sectional network analysis utilized a convenience sample of 391 treatment-seeking patients with SUD in a specialized addiction psychiatric clinic. We measured drug and alcohol use, dependence features and psychopathology using clinician-rated scales. Personality and impulsivity were measured using self-report instruments. LASSO network, centrality indices and network stability were estimated. We also estimated the relative importance of the network nodes in determining levels of drug and alcohol use and dependence severity. The domain-level LASSO network of additive behaviour, psychopathological variables, traits of the Big Five Inventory (BFI) and impulsivity formed a highly connected network. BFI-neuroticism lied at the centre of the network with the highest closeness index. Depressive symptoms, anxiety symptoms and 'general' symptoms in the Positive and Negative Syndrome Scale showed highest expected influence and predictability. The mean predictability of the network suggested a self-sustaining system. The three psychopathological nodes significantly determined the variance of drug use and dependence severity. The network structure of SUD is influenced by anxiety and depressive symptoms. Clinicians should detect and intervene these symptoms to break the self-sustaining system of SUD.