The experiment was undertaken to investigate the retention of clnomated-copper-boron (CCB) preservatives in Pitali (Trewia nudiflora L.) wood applying soaking as well as diffusion method. The assessments were applied for 5, 7, 9 and 11 days for both the method. The retention of the preservatives were recorded 12.29 kg/m³, 14.97 kg/m3, 15.11 kg/m³ and 15.72 kg/m³ in Pitali wood where soaking method applied. Moreover, retention was found 11.43 kg/m³, 23.49 kg/m³, 24.14 kg/m³ and 25.38 kg/m³ in Pitali when diffusion method applied. In case of both the method, highest retention was recorded 15.72 kg/m³ and 25.38 kg/m³ in pitali wood after 11 days. Considering the Standard of Bangladesh Standards and Testing Institution (BSTI), i.e., 15.72 kg/m³ and 25.38 kg/m³ in Pitali can meet the suitability of the study. According to BDS code, the required retention of CCB is 8-16 kg/m³.