For a connected graph G, let L(G) denote the maximum number of leaves in a spanning tree in G. The problem of computing L(G) is known to be NP-hard even for cubic graphs. We improve on Lorys and Zwoiniak's result presenting a 5/3-approximation for this problem on cubic graphs. This result is a consequence of new lower and upper bounds for L(G) which are interesting on their own. We also show a lower bound for L(G) that holds for graphs with minimum degree at least 3.