The purpose of this research is to present the geometric characterization of the measured porosity of the Upper Triassic dolomites of Žumberak Mts., through the analysis of several geometric parameters. Pore parameters were analyzed on microphotographs of impregnated thin sections in scale. Microphotographs have been converted into binary photographs by image processing techniques. A total of 13,938 pores were isolated and analyzed. Effective porosity of all analysis geological formations and facies are in the interval from 0,314 % to 4,564 %. Some samples had higher measured porosity, but they also contained fractures so measured porosity was not only depositional and diagenetic but also microfracture porosity. The analyzed parameters are: Pore surface, pore circumference, circularity, AR, Roundness, Solidity, Feret AR, Compactness and Fractal dimension. Each of the measured parameters quantifies the geometry and complexity of the pore shape in a certain way. The area and extent of the measure are the dimensions of the pores. Circularity is a parameter that describes how much is the analyzed object like the shape of a circle. Roundness, AR, and Feret AR are parameters that describe how similar a pore is to an ellipse and quantify pore elongation. The Solidity and Compactness quantify pore irregularities or "roughness". The fractal dimension quantifies the property of self-similarity and thus the complexity of the pore shape. The results indicate that the pores are generally less than 1 mm with a small number of pores that are larger and can be considered extremes that significantly affect the appearance of histograms of surface frequencies and pore circumferences. Other parameters that quantify the shape and complexity of the pores are at the expected intervals and indicate that the pores are generally elongated with the longer axis of the corresponding ellipse 1.7 to 2 times larger than the shorter axis. Higher values of circularity and lower values of Roundness indicate that the pores, regardless of elongation, are closer to the shape of a circle than ellipses. Parameters that quantify pore irregularities, ie. "roughness", "Solidity", Compactness, and Fractal dimension have similar distributions and their values indicate a pronounced complexity of the pore geometry. This is especially confirmed by the fractal dimension values. Image Processing techniques in microphotographs analysis is a very powerful toll for collecting large number of exact data. The proposed methodology is very useful in quantification of pore geometry parameters.