Electrical impedance (EI) is the resistance to the flow of alternating electric current through a tissue. It is dependent on the structure and the chemical composition of the tissue and is therefore used for diagnostic purposes, primarily for changes in the skin. Application of EI in diagnostics related to the oral mucosa has not been sufficiently evaluated scientifically. The purpose of the study was to determine the reference values of EI on healthy oral mucosa, and to evaluate the feasibility and reproducibility of the method. The aim also was to determine the effect of demographic and clinical factors (gender, age, smoking, amount of saliva, pressure of the electrode) on EI values. The study included 101 subjects divided into three groups: 20-40 years, 40-60 years and over 60 years. Inclusion criteria were clinically normal oral mucosa and the ability to read and understand the text of the informed consent. EI values were measured by a specially designed device three times at one-week intervals at 14 measuring points in the oral cavity (7 points on its left and right side, respectively). The intraoral sensor consisted of a system of concentric electrodes that adhered to the mucous membrane through application of varying degrees of negative pressure (250° or 350 MB). It was connected to the measuring device NI USB-6251 (National Instruments®, Austin, USA) connected via USB to a laptop. The measurement programme developed on the basis of the LabView 8.5.1. software package (National Instruments®, Austin USA) converted the electrical impulses from the device into digital records and stored them in the database. Statistical analysis was performed using the SPSS ver. 20 software (IBM Inc, USA). The highest values of EI were recorded on the mucosa of the hard palate, and the lowest on the dorsum of the tongue. No statistically significant differences in EI values between the left and right side were established. EI values were found to decrease with age, and to be significantly higher in women than in men. This finding needs to be verified and clarified in future research. In nonsmokers, significantly higher EI values were found only in the mucosa of the upper lip. The amount of saliva had no effect on the measured values. The pressure exerted on the mucous membrane by the electrode did affect the measured values - applying higher negative pressure resulted in statistically significantly lower values. No statistically significant differences were found between individual measurements in any of the subjects. The method described in the study makes it possible to measure EI values at each point of the oral mucosa. The method is simple and easily applicable, and provides reproducible and stable results, which in turn opens the possibility of using it for non-invasive differentiation of healthy oral mucosa from various pathological conditions.