Aim: Periappendicular inflammatory mass (PIM) defined as a mass located at the right lower quadrant of the abdomen due to inflammation, and cannot clearly distinguish from borders of appendix. The aim of this study is evaluating the PIM.Method: The patients who hospitalized for PIM evaluated retrospectively. Patient’s age, gender, length of hospital stay (LOS), performing colonoscopy,comorbidity, etiology, and treatment evaluated. Also, etiology elaborated with age, gender, LOS, treatment, levels of C-reactive protein (CRP), whiteblood cells, neutrophil % (Neu%), and performing colonoscopy.Results: One hundred fourty four patients were included to study. The mean age was 41.35±17.9 years, and 54.2% of the patients were male.The mean LOS was 4.2±2.6 days. Colonoscopy performed only 28.5% of the patients. The most common etiology was plastron appendicitis (PA)(75%), and 32.4% of the PA was with abscess. 67.3% of the patients were treated conservatively (medical treatment or percutaneous drainage),and the rest treated surgically. The most common surgical approach was diagnostic laparoscopy and drainage. Malignancy reported at two right atage, LOS, treatment, CRP, Neu%, and colonoscopy between etiologies were statistically hemicolectomy patients. The most common comorbiditieswere hypertension and diabetes (12.5%, and 8.3%, respectively). 44.4% of PIM had negative ultrasonography, 71.5% had positive CT imaging. Thedifferences significant (p<0.05).Conclusion: Not only plastron appendicitis but also Crohn’s disease, diverticulitis, mucocele, and malignancy should keep in mind when evaluatingthe inflammatory mass of the right lower quadrant. Age, LOS, treatment, inflammatory markers, and performing colonoscopy significantly vary dueto etiology.