There has been some concern about the impact of predatory publishers on scientific research for some time. Recently, publishers previously viewed as ‘predatory’ have established their bona fides , at least to the extent that they are included in impact scores such as the field-weighted citation impact (FWCI). These are sometimes called grey publishers (MDPI, Frontiers, Hindawi). We show that the citation landscape for these grey publications is significantly different from the mainstream landscape and that affording grey publications the same status as mainstream journals may significantly distort metrics such as the FWCI.