We deal with the so-called Ahlfors regular sets (also known as $s$-regular sets) in metric spaces. First we show that those sets correspond to a certain class of tree-like structures. Building on this observation we then study the following question: Under which conditions does the limit ${lim}_{\epsilon \to 0+}{\epsilon }^{s}N(\epsilon ,K)$ exist, where $K$ is an $s$-regular set and $N(\epsilon ,K)$ is for instance the $\epsilon$-packing number of $K$?