Introduction: Oral diseases may be aggravated in HIV/AIDS patients depending on their immune response and lymphocyte levels. Objective: Describe the relationship between CD4 T lymphocyte levels and the main oral lesions in HIV/AIDS patients from Hipólito Unanue National Hospital in Lima, Peru, during the year 2018. Methods: An analytical cross-sectional study was conducted of 65 hospitalized patients from July to October 2018. The patients underwent oral clinical examination. Evaluation was performed of the presence of HIV/AIDS-related oral manifestations, and CD4 T lymphocyte levels were classified into three categories: > 500 cell/mm3, 200-500 cell/mm3 and < 200 cell/lmm3. Results: Of the total patients studied, 70.8% were not under antiretroviral treatment at the moment of the examination. Average CD4 T lymphocyte level was 237.65 cell/mm3, with higher results among women. 56.9% of the patients had oral lesions. Males were more commonly affected (91%). The most frequent lesion type was oral candidiasis (44.6%), whereas the category presenting the highest frequency of oral lesions was < 200 cell/mm3 (38.5%; p < 0.05). Conclusions: Male patients presented the largest number of oral lesions associated to low CD4 T lymphocyte levels. Most of the oral lesions were found at a CD4 T lymphocyte level < 200 cell/mm3. Oral candidiasis was the lesion most commonly found by the clinical examination.