In 1989 – 1991, after the collapse of the Soviet Union, it was an auspicious moment for structural changes in education systems in the new independent countries, which had been under control of the Soviet government for a long time. About three decades have passed since the beginning of the education reforms in the post-Soviet countries and several generations who studied within the framework of the reformed systems starting from the first grade have already grown up. Therefore, it is relevant to estimate the results of the reforms. One of the possible measures for estimating the results of the education system or education reform is the change in population literacy within certain education systems. The purpose of the article is to compare the results of education reforms of the post-Soviet countries based on the population literacy considered as a result of former learning. The data of the Programme for the International Assessment of Adult Competencies (PIAAC) organised by the Organisation for Economic Cooperation and Development (OECD) are used for literacy comparison. The OECD PIAAC survey databases of Lithuania, Estonia, Russia, Poland, the Czech Republic, Slovakia and Slovenia were used for comparison of the results of the reforms implemented in the post-Soviet countries. Data analysis showed that at the lower and upper secondary education levels, the most positive results of the education reform were observed in Lithuania, while in Russia, the results were negative.