Chronic rhinosinusitis (CRS) presents with two basic phenotypes, CRS with (CRSwNP) or without nasal polyps (CRSsNP). The present study’s objective was to evaluate the clinical characteristics in a Greek population of CRSwNP patients and their relation to the frequency of CD4⁺ and CD8⁺ T cells as well as the CD4⁺/CD8⁺ ratio as prognostic biomarkers. Thirty-three adult CRSwNP patients were recruited at the ENT Department of “G. Papanikolaou” General Hospital of Thessaloniki. Tissue samples from nasal polyps were collected during functional endoscopic sinus surgery. Hadley’s nasal endoscopy scores, preoperative Lund-Mackay CT scores, and 22-item Sinonasal Outcome Test, were recorded for each patient. The presence of CD4⁺ and CD8⁺ lymphocytes was evaluated in tissue sections by immunohistochemistry. Blood eosinophil and neutrophil counts were also included in the analysis. All data were analyzed with SPSS (version 21.0). Twenty-one males and 12 females were included in the analysis with mean age of 49.5 ± 14.5. LMS ( P < 0.001, r = 0.961) and HES ( P = 0.001, r = 0.54) were both positively correlated with SNOT 22. Hadley’s endoscopic score was also positively correlated with Lund-Mackay CT score ( P < 0.001, r = 0.674). Absolute count and percentage of eosinophils were positively correlated with LMS ( P = 0.003, r = 0.513, P = 0.002, r = 0.527 respectively) and HES ( P < 0.001, r = 0.622, P = 0.004, r = 0.497 respectively). Ιn a subgroup analysis, CRSwNP patients with blood eosinophils >5%, LMS and SNOT 22 were negatively correlated to CD4⁺ cells ( P = 0.029 r = −0.654, P = 0.043, r = −0.618, respectively). In CRSwNP patients with CD4⁺/CD8⁺ ratio <0.3, CD8⁺ T cells were positively correlated with the absolute count and percentage of eosinophils ( P = 0.042, r = 0.684, P = 0.036, r = 0.699 respectively). In this study, we recognized the potential importance of nasal CD8⁺ T cells in the pathophysiology of CRSwNP patients, also characterized by eosinophil accumulation. Furthermore, the patients’ clinical characteristics were also positively correlated with the eosinophilic inflammation and the severity of the disease.