BACKGROUND: The Modified Mallampati classification is a simple, easily reproducible, widely used test, which is performed with the patient in a sitting position with the tongue protruded and without phonation. It is more convenient when an assessment of modified Mallampati classification is performed while the patient is in a supine position on the operating table. The purposes of this study are to compare the correlation between the modified Mallampati classification in the supine and sitting positions, and the laryngoscopic grades of Cormack and Lehane. METHODS: The data were collected from a total of 224 (98 male) patients older than 18 years of age undergoing elective surgery. The assessment of the modified Mallampati classification was performed two times to the same patient; once while the patient was in a sitting position, and the 2nd time in a supine position on the operating table. Assessment of the modified Mallampati classification in a supine position was performed in the absence of tongue protrusion and the presence of performed phonation. RESULTS: There were significant correlations between assessments of the modified Mallampati classifications (sitting position and supine position) and the laryngoscopic grades of Cormack and Lehane. CONCLUSIONS: Assessment of the Mallampati classification in the supine position had a significant correlation with laryngoscopic grades. We suggest that assessment of Mallampati classification in the supine position can be used as one of the predicting factors for difficult intubation.