Faced with the rapidly growing increase of designer drug abuse, particularly amongst the younger generation, various legislative strategies are currently employed world-wide for tackling this problem – however with mixed results. The key issue is that the producers of DDs are able to either exploit existing legal substances intended for other uses, but which have been found to possess psychoactive properties, or to synthesise new psychoactive substances by introducing chemical modifications, often very minor ones, thereby avoiding the prohibited use of chemicals included on any banned lists. Some countries opt to ban new drugs as and when shown or considered to be harmful, while others introduce sweeping bans based on chemical structure. Nevertheless, an ever increasing diversity of new DDs are constantly appearing on domestic and Internet markets. Poland, together with the UK and Eire, has placed temporary bans on all DDs whenever they have been identified, thus enabling sufficient time for assessing their potential hazards to health. Part of this ‘holding’ strategy entails a thorough review of the scientific literature, including expert opinion when direct evidence is lacking, as well as information received from EU support organisations Europol and the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). This paper, in two parts, therefore aims to provide an up-to-date summary review of available scientific evidence on the harm caused by the six main chemical groupings of DDs found in drug seizures of illegal products recently made in Poland. The first part is devoted to Cannabinoids and Cathinones derivatives. Ensuing legislation can therefore be rapidly formulated to make the bans permanent as appropriate.