Open government has become an important topic in democratically developed societies. Its key aims are to increase transparency, citizen trust and public participation. Against this background, the article focuses on perceived barriers opposing the introduction of open government data. On the basis of cognitive theory and a literature review, the essential factors that impede public servants in implementing open government data are conceptualized and summarized in a model. The perceived risk-based attitude of public servants is identified as the main barrier. Other significant obstacles include perceived legal barriers, perceived hierarchical structuring of authorities, perceived bureaucratic decision-making culture and perceived organizational transparency.