Background/aim: Dental Implant therapy has become an integral part of daily practice due to its high successrate but surgical mishaps, complications and damage of vital anatomical structures do occur. If proper diagnosis and treatment planning is done then implant surgeries can proceed uneventfully and can fulfil both the functional and aesthetic demands after osseointegration. The aim of this study was to determine the longest upright and tilted implants allowed to be placed in three posterior mandibular teeth areas in case of Immediate Implant Placement (IIP) with respect to a safe distance from the inferior alveolar canal (IAC) and the submandibular fossa, using cone beam computed tomography (CBCT). Materials and Method: The 209 CBCT scanswere reviewed retrospectively of the subjects. The following were measured: distance from the tooth apex to the IAC, buccolingual width of the mandible which was determined at the axial section nearest to the middle of tooth?s mesiodistal width, classification of mandibular cross-sectional morphology as per Sammartino et al (2008) and Chan H-L (2011),upright and tilted implant placement simulation, tilting anglethat allowed placement of the longest implant and availability of buccal and lingual cortical plate. Results: As we progress posteriorly i.e., from second Premolar (PM) to Second Molar (M) the distance from tooth apex to IAC decreases significantly. The mean value between the teeth is increasing significantly. The mandibular cross-sectional ridge types are U (undercut), C (convergent); P (parallel) had a prevalence rate of 65%, 23%, and 14% respectively. The available width for both buccal and lingual cortical plate increased significantly from 2PM to 2M. For the moreposterior regions the tilting angle was greater in orderto place the longest implant without causing any lingual perforation and damage to vital anatomic structures like the IAC. Conclusions: Within the scope of this study, we have concluded that the distance from the tooth apex to IAC decreases in molar region as compared to premolar region. Whereas, buccolingual width of the mandible is greater in molars as compared to the premolars. Mandible has a tendency to be classified as ?undercut? in more posterior regions. Therefore, there is a need for careful attention when the placement of an immediate implant is planned in this area. Alternative treatment option to avoid the violation of the lingual plate perforation includes the use of implant tilting. More posterior regions resulted in a restriction to place shorter implants in comparison to more anterior regions.