The value of real estate is an extremely important information for the functioning of today's society. This information is used by public authorities, banks, investors and private individuals. People who's work involves assessing the value of real estate are called appraisers. In the Republic of Croatia, the area of real estate valuation is defined by the Real Estate Valuation Act and the Real Estate Valuation Regulations. There are several methods for estimating the value of a real estate property, such as the comparative, the revenue and the cost method. The comparative method is based on comparing the value of the property with the value achieved by a sufficiently similar property on the market. The revenue method is based on the fact that the value of the property depends on the income that this property can generate. The cost method is based on the fact that the property is not worth more than the cost of buying land and building on it. The above methods refer to individual assessments. In mass assessments, there are multiple regression analyses (MRAs), neutral network analyses (ANN) and expert systems analyses (ESAs). Mass assessments are the basis for the introduction of property tax and, consequently, a fairer taxation system. A major step forward in data systematization was achieved with the introduction of the "eNekretnine" system. In the Republic of Croatia, the task of implementing knowledge in the field of real estate valuation has been given to the Ministry of Physical Planning, Construction and State Property, where it is a great responsibility to manage and protect the premises as one of the most valuable Croatian resources.