Water accounting is an important tool for water managers. Many studies use official water accounting data or similar data for their assessment. In particular, large-scale studies or water footprint studies have limited opportunities for -in-situ- data collection. In many cases, the processors of studies do not know the origin of the data and their limitations. Water accounting data are very often used for decision-making process, water resource management, and planning in the water sector. This article tries to answer the question ´How truthful are water accounting data?´ For this task water accounting in the agriculture sector in the Czech Republic was selected. The data on water withdrawals for the agriculture purposes was analyzed and compared with water needs estimation based on additional data on agricultural production.