The changing security environment has led to the development of com¬prehensive security approaches, strategies and policies. The ‘Holistic approach’ has become an academic and practical mantra. This paper argues, however, that comprehensive security approaches face serious obstacles to their practical implementation. The critical evaluation of several examples confirms that the implementation phase is a weakness of comprehensive approaches and that a truly comprehensive and holistic approach seems to be beyond the implemental capacities of our security systems. Multi-sectoral and multi-level comprehensive approaches become less comprehensive when implemented in practice or even cannot be implemented due to existing narrow perceptions of security or narrow and short-term interests. The trans-sectoral second-, third- and fourth-order effects of proposed security measures are hardly considered or not considered at all. There is no consensus on what exactly comprehensive means, while prioritisation of some areas in the national security policy leads to de-prioritisation of other areas and new vulnerabilities, inter-organisational and cross-sectoral cooperation faces serious limits, threat, risk and vulnerability assessments are not really comprehensive, etc. This paper finishes with recommendations on what to do about these serious limits on the implementation of comprehensive security.