One of the main objectives of nowadays ecology is the control of nitrogen dioxide level in the atmosphere. This problem can be solved by the use of semiconductor gas sensors based on semiconductor metal oxides such as In2O3, ZnO, SnO2, WO3, TiO2 [1]. Nanocrystalline In2O3 is a perspective material for utilizing in gas sensors. For example, in comparison with SnO2 it provides an advantage of higher baseline conductivity in air. The number of adsorbed molecules depends on the area of specific surface. One of the ways to increase the specific surface area and, consequently, the adsorption capacity is the reduction of nanocrystals size which, in its turn, can lead to essential changes in electric properties of the materials. In this case there is a challenge to study conduction mechanisms in nanocrystalline indium oxide with small sizes of nanocrystals. Measuring the frequency dependences of conductivity is an informative method of investigating the mechanisms of charge carriers transport. Thus, the purpose of this work is to study the influence of nitrogen dioxide adsorption on frequency dependences of conductivity in nanocrystalline indium oxide with different sizes of nanocrystals (7-20 nm). Nanocrystalline samples of In2O3 were prepared by sol-gel method with subsequent annealing at various temperatures (T=300-700ºC) and deposited on glass substrates with thickness of several micrometers. To measure the electrical characteristics, gold contacts were vapor-deposited on top of the films. Measurements of thermopower have shown that samples possess n-type conductivity. Frequency dependences of conductivity are measured by impedance analyzer HP 4192A in the frequency range from 5 Hz to 13 MHz at different temperatures (300 K and 420 K). Adsorption of nitrogen dioxide was performed by generator GDP-102 at various concentrations (2-8 ppm). The analysis of full impedance hodographs have shown that for all studied samples under various conditions (at different concentration of NO2 and temperatures) the equivalent scheme can be presented in the form of consecutively connected resistance Rc and parallel chain consisting of resistance Rs and capacitor Cs. The parallel RsCs-chain can be identified with resistance Rs and capacitor Cs of a sample, and additional resistance Rc is identified with resistance of contacts. Besides we will note that resistance of the sample exceeds resistance of the contacts by several orders of magnitude. We can see that conductivity reduces under NO2 adsorption and it decreases not linearly under linear growth of NO2 concentration. Besides, it should be noted conductivity of In2O3 returns to the initial value when gas flow has been turned off. The decrease of In2O3 conductivity with NO2 adsorption can be explained by reduction of free electrons concentration and growth of potential barriers heights on the boundaries of nanocrystals. The height of potential barriers could have changed due to recharging surface states on the boundaries of nanocrystals under the adsorption.