In this paper, we compare the interaction, of lithium and sodium with a range of carbon materials in electrochemical cells. Through wide angle in situ X-ray scattering studies, we demonstrate that both lithium and sodium can be inserted into the interlayer space in disordered carbon materials. This insertion process is accompanied by an increase in the interlayer spacing in these materials. Small-angle in situ scattering studies are presented to clearly show the insertion of lithium and sodium into nanopores within disordered hard carbons. We also show that very little, if any, sodium can be inserted into graphitic materials in contrast to the large capacity seen for lithium insertion.