Diagnosing a tumor is a benign or a malignant one plays an important role in the decision of its treatment strategy. To differentiate these two kinds of bladder cancer the authors count on anatomopathologic, ultrasonic or CT scan results. The ultrasonic result is less believable and the authors haven't had CT scan for all hospitals, mostly in provincial hospitals. The authors studied on the changes of lymphocytes in peripheral blood of 92 patients, divided into 4 groups (according to the anatomopathologic result): 20 patients with superficial bladder cancer (group II), 15 patients with invasive one (group III), 28 patients with mouth squamous cancer (group IV), and 29 healthy persons (group I). They realized that there was no significant difference of the average ratio of CD4/CD8 between group I and group IV (p=0.780). On the contrary, the difference of this ratio between group I and group II as well as group I and group III is statistically significant (p= 0.000). The authors conclude that this average ratio of CD4/CD8 can be used as a mean to differentiate in diagnosing in bladder cancer but not in mouth squamous cancer.