Although the large white-headed gull group (genus Larus) has long been a model in speciation studies, the systematic status and evolutionary relationships of many of its taxa remain unresolved. We used mitochondrial DNA control region and cytochrome-b gene sequences in an attempt to resolve some of those uncertainties. In contrast to previously published results based on nuclear markers, mitochondrial DNA was found to be strongly structured among species, indicating that mitochondrial gene flow is very low. Phylogenetic relationships remain largely unresolved, mainly because of the low amount of variation between species. Horizontal transfer of mitochondrial lineages is demonstrated or suspected between most taxa and obscured the reconstruction of the history of the group. The Mediterranean form michahellis was as differentiated from the other western European species as these are from each others, confirming it is neither conspecific with L. fuscus nor with L. argentatus. The forms fuscus and graellsii do not show any significant differences in haplotypes frequencies, arguing for their subspecific status.