The relation between information science and library science has been debated for decades, and even attempts at utilizing methods generally acknowledged as robust for the purpose of mapping research fields have yielded results with large variations. Therefore, a set of citation analyses was performed, comparing the results of analyses on information science and library science separately but also as a joint library and information science (LIS) field. Although there are large differences, not the least in the author-level analyses, the patterns in the citation data support the concept of a joint LIS field with information science and library science being the two main subfields; many of the variations in the analyses are caused by the interdisciplinary nature of LIS, reflected in, for example, variations in citation practices in the different subfields.