Polymeric nanoparticles have a great potential as carriers for targeted drug delivery and as contrast agents and the interest and research in the field of nanoparticles for drug delivery and contrast agents has exponentially increased. Such carriers have the potential of high loading capacity, increased therapeutic index, co-delivery of multiple drugs, multifunctionality and high stability. In spite of all these advantages only few products are on the market today or in clinical trial phase 2 and 3. What is the reason for this and which scientific research efforts should be focused on in the near future to shorten the time for this lab to clinic transition and to overcome the main challenges? Standardization, quantitative documentation, reproducibility, scale-up, competitive price and toxicity of the particles themselves or stabilizers and other additives are some of the challenges. In this presentation, examples from own research and literature will be given to illustrate the main challenges and to create a basis for a plenum discussion. Hopefully, the discussion will lead to 2-3 priority research items for the SRA up-date in the field of drug delivery.