Abstract: Geological storage of CO2 is one of the measurements for reducing it's concentration in the atmosphere. Due to their big surface, empalcement near great industrial sources of CO2 and trapping mechanisms which occure during distinct periods of time the greatest storage potential is estimated in deep saline aquifers. However, there are many uncertainties in the estimates of the storage capacity of these large bodies of rock. Uncertainties are mainly related to the lack of data. In the PhD theseis made by Iva Kolenković, Poljana sandstones are isolated as a potential storage facilities in the western part of Sava Depression.These sandstones are also characterized by a small number of data. One of the critical parameters during the estimation is porosity. Object of this paper was to explore the possibility of calculating the weighted averages of porosity. With porosity, effective thickness was selected as a weight parameter, so that wells with greater effective thickness have a bigger impact on the assessment of those with less. The main intention of this procedure was to avoid construction of the porosity map based on such small amount of data (20 wells). Also, this paper examined the possibility of division of the area of research. The previous papers discretized the aquifer area with grid of blocks from whose centers were determined values of the parameters from the corresponding maps. This procedure is complicated and requiers a lot of time. Having in mind that due to lack of data the results of this level of research can be used only for directing the future researches and can not be directly applied, it would be very useful to find a simpler way of assessment provided that the results still do not differ too much. Therefore are designed five new methods of calculating the storage capacity. Every one of them is explained and illustrated with related map of effective thickness and tabular calculation. Also, an diagram and a series of tabular presentations of the distribution of data were designed to facilitate comparisons of results,. According to the final results of the storage capacity, presented simplification of calculation can be considered acceptable and find application in the first stage of research in determining the potential of deep saline aquifers for CO2 storage.