The relationship between substance use disorders (SUD) and brain deficits has been studied extensively. However, there is still a lack of research focusing on the structural neural connectivity in long-term polydrug use disorder (PUD). Since a deficiency in white matter integrity has been reported as being related to various parameters of increased psychopathology, it might be considered an aggravating factor in the treatment of SUD. In this study we compared two groups of PUD inpatients (abstinent: n = 18, in maintenance treatment: n = 15) to healthy controls (n = 16) with respect to neural connectivity in white matter, and their relation to behavioral parameters of personality factors/organization and attachment styles. Diffusion Tensor Imaging was used to investigate white matter structure. Compared with healthy controls, the PUD patients showed reduced fractional anisotropy (FA) and increased radial diffusivity (RD) mainly in the superior fasciculus longitudinalis and the superior corona radiata. These findings suggest diminished neural connectivity as a result of myelin pathology in PUD patients. In line with our assumptions, we observed FA in the biggest cluster as negatively correlated with anxious attachment (r = 0.36, p < 0.05), personality dysfunctioning (r = -0.41; p < 0.01) as well positively correlated with personality factors Openness (r = 0.34; p < 0.05) and Agreeableness (r = 0.28; p < 0.05). Correspondingly these findings were inversely mirrored by RD. Further research employing enhanced samples and addressing longitudinally neuronal plastic effects of SUD treatment in relation to changes in personality and attachment is recommended.