The lichenicolous Phoma species on Cladonia are revised. A statistical analysis of the conidial size suggests that three species are involved: P. cladoniicola sp. nov. a common and widespread species in the Northern Hemisphere occurring on a wide range of Cladonia species; P. foliaceiphila sp. nov. known from C. foliacea and C. fimbriata in Europe; and P. grumantiana sp. nov. known from C. symphycarpia and C. mateocyatha in Svalbard and the USA.