Soil reaction, expressed as a pH value, is an indicator of acidity or alkalinity. The soil acidic reaction causes increased mobility of aluminium in the soil and can have negative effects on root growth. Plants grow and develop in soils of different soil reactions, but the optimum soil reaction is between slightly alkaline and slightly acidic. The aim of this research was to determine the impacts differences between the effects of biochar and sugar factory waste lime on soil reaction in acid soils. The research was carried out on stationary field trials at two locations on acid soils in Osijek-Baranja and Virovitica-Podravina County, Croatia. The treatments were: C - control, B1 - 5 t ha^-1, B2 - 10 t ha^-1, B3 - 15 t ha^-1 of biochar and L optimal dose of sugar factory waste lime that was calculated for each field trial location. Two steps of sub factors were also applied, F0 - without fertilization and F1 – with recommended fertilization. Soil samples were taken in V3 and silking stages of maize growth from 0-25 cm. The average soil pH value in V3 stage of maize growth was 5.42 and in silking was 5.93. The highest pH values in both stages of maize growth were measured in treatment with liming. The lowest hydrolytic acidity was measured at the liming treatment, while all other treatments had a significantly higher value compared to lime. sugar factory lime is optimal conditioner if we want fast and cheap raise in soil pH values, but it must be noted that together with liming we usually must implement many other soil restauration measures, like humization, especially in degraded soils.