In this paper we consider the relation between random sums and compositions of different processes. In particular, for independent Poisson processes N (alpha) (t), N (beta) (t), t > 0, we have that , where the X (j) s are Poisson random variables. We present a series of similar cases, where the outer process is Poisson with different inner processes. We highlight generalisations of these results where the external process is infinitely divisible. A section of the paper concerns compositions of the form , nu a(0,1], where is the inverse of the fractional Poisson process, and we show how these compositions can be represented as random sums. Furthermore we study compositions of the form I similar to(N(t)), t > 0, which can be represented as random products. The last section is devoted to studying continued fractions of Cauchy random variables with a Poisson number of levels. We evaluate the exact distribution and derive the scale parameter in terms of ratios of Fibonacci numbers