Statement of problem: Unfavorable crown root ratio is linked to mobility, as a result mobile teeth are excluded from serving as abutments which complicates the treatment plan. objective: To find if there is true correlation between crown root ratio(C/R) and tooth mobility (TM) by utilizing cone beam computed tomography (CBCT) and periotest. Materials and methods: The records of 72 patients who attended BAU dental clinics for orthodontic treatment or oral implant placement between 2011 and 2013 were gathered based solely on the availability of CBCT records for single rooted teeth. Only 29 records that fulfilled the inclusion criteria were selected. These records belonged to orthodontic patients with mild occlusal discrepancy who haven’t started their treatment yet, and to those requesting tooth replacement with implant retained restoration but having enough posterior stops. All included participants were healthy, aging from 25 to 35 years, having good oral hygiene and acceptable functional occlusion. Patients were asked to participate in the study and 26 subjects recalled (18 males and 8 females). All permanent upper anterior teeth and lower canines and premolars with fully developed roots were assessed for TM and their C/R were measured. The teeth included in the study were 278 single rooted teeth obtained from the 26 CBCTs were included in the study. The data was coded and entered using the statistical package SPSS version 20. The data was summarized using descriptive statistics. results: The mean C/R was 0.64 (+ 0.13) and mean periotest reading was -0.61 (+ 3.34). The maximum C/R was 1.51 and the minimum was 0.30, with a median of 0.62 and standard deviation of 0.14. The maximum periotest value was 22.8 and the minimum was -5.90 with a median of -0.93 and standard deviation of 3.35.Using SPSS, we get: r = 0.616. Pearson’s correlation coefficient revealed a statistically significant moderate and positive correlation between C/R and TM at 0.01 level. Conclusions: There was a positive and moderate correlation between crown root ratio and mobility in single rooted teeth with healthy periodontium. Keywords: Tooth mobility, Crown root ratio, CBCT, Periotest.