Phylogenetic trees based on group I intron sequences and on internal transcribed spacer (ITS) sequences of mycobiont ribosomal genes were calculated and compared. Eight cetrarioid and four non-cetrarioid species of the Parmeliaceae were compared. The phylogeny based on group I intron sequences is partly congruent with the ITS sequence phylogeny. Group I intron sequences are presumably less informative for infragenic studies. The introns have a length of 214–233 nucleotides, and differ at up to 33% of the bases between species. All introns analysed are located between the positions 1516 and 1517 of the fungal 18S ribosomal RNA gene. Cetrarioid lichens form a non-homogeneous group within the Parmeliaceae according to both group I intron and ITS sequences.