This paper deals with the complex problem of how to evaluate the parameters of the structure in circulating fluidised beds. Some aspects of this problem have arisen from the introduction of circulating fluidised bed boilers. The distributions of particle concentration and particle velocity reflect the random behaviour of particles in a combustion chamber. The level of particle velocity-while the boiler is in operation-has an impact on the combustion process, kinetics and heat transfer, and also on the erosion processes on the heat surfaces. A linear combination of double Maxwellian distributions has been assumed to describe a component of the distribution of particle velocity. This assumption allows us to calculate statistical moments in a different way, e.g. the mean particle velocity, granular temperature, etc. Additionally, the local structure of a circulating fluidised bed has been presented.