We predicted: (i) a significant association between baseline measures of each neuroimaging technique and longitudinal decline in cognition; (ii) partially independent and additive effects of MRI and PET measures on cognitive decline, assessed with all modalities together in a single multivariate model; and (iii) that the molecular markers of baseline tau and neuroinflammation PET would be more informative than structural MRI on longitudinal cognitive deterioration in Alzheimer’s disease. The gene discussed is MAPT; the disease is Alzheimer disease.