<h4>Purpose</h4>Our aim was to investigate brain metabolic connectivity, as assessed via [<sup>18</sup>F]FDG-PET, in ALS patients carrying the C9ORF72 expansion (C9-ALS).<h4>Methods</h4>We compared brain metabolism of C9-ALS and patients without mutations of the main ALS-related genes (ctrl-ALS) through the two-sample t-test model of SPM12. Here, C9 is linked to amyotrophic lateral sclerosis.