Publisher Summary This chapter highlights the use of property models in solving various types of chemical product design problems. It focuses on the estimation of properties and their corresponding model rather than the solution of the design problem. The chapter is divided into three main sections: (1) first a general definition of the property model needs for typical chemical product design problems is discussed. (2) Then two examples of special property models that can be generated or adapted for the estimation of the needed (target) properties are presented. (3) The chapter highlights the application of the property models for specific chemical product design problems. Contrary to process design where a set of properties need to be estimated for a fixed number of identified components and their mixtures (solutions), in chemical product design, a similar set of properties may need to be estimated for a wide range of chemicals (species) and their mixtures. In many cases, identities of some of the chemicals are known. Therefore, in terms of components and their mixtures, while in process design a fine-tuned (to the component system of the process) parameter set of a property model needs to safely interpolate, in product design a general parameter set (of wide application range) of the same property model needs to safely extrapolate.