Introduction: Diagnostic discrimination between acute appendicitis (AA) and mesenteric lymphadenitis (AML) may require more diagnostic tests or great skill after excluding other diagnoses. This study aimed to make a differential diagnosis between AA and AML patients with previous and new parameters and to examine which parameters should be taken into account regarding whether the AML patient should be hospitalized or discharged. Material and methods: One hundred and twenty-three AML and 134 AA patients, randomly selected, were included in the study. Demographic, clinical, and laboratory data of all subjects were analyzed. Ultrasonographic and rarely computed tomography examinations evaluating for the enlarged lymph nodes with the shortest diameter in the right lower quadrant of the AML patients were performed. Also, the erect abdominal radiographs (EAR) of AML and AA patients were evaluated. Results: While there was no statistically significant difference in age or gender, C-reactive protein, white blood cell count, monocyte percentage as well as symptoms between the AA and AML groups (p > 0.05), neutrophil and lymphocyte percentage, appearance of EAR and L/M ratio were significantly different between the two groups (p < 0.05). There was no correlation between the short-axis diameter of the mesenteric lymph node and clinical and laboratory findings in the AML group (p > 0.05). Conclusions: Based on the results with ROC curve analysis, we propose to take into account the L/M ratio and the EAR from the parameters in the differential diagnosis between AA and AML in addition to previously reported parameters. Also, we recommend that the same features may be used to decide whether AML patients under observation are hospitalized or not.