Some analogy exists between cognitive impairment in hypoxemic patients with chronic obstructive pulmonary disease (COPD) and Alzheimer's disease (AD). We purposed to verify whether the analogy extends to the cerebral perfusion pattern. Ten normal subjects, 15 COPD patients with and 18 without hypoxemia, and 15 patients with mild AD matched for age and educational level underwent brain perfusion single photon emission computed tomography (SPECT) and neuropsychological assessment. Normal subjects and non hypoxemic COPD patients had comparable perfusion patterns. The average perfusion decreased from non hypoxemic to hypoxemic COPD and, then, to AD patients. Hypoperfusion of associative areas was the hallmark of AD, whereas the average perfusion of anterior cortical and subcortical regions did not distinguish AD and hypoxemic COPD patients. Both COPD groups scored higher than AD patients (p </= 0.01) in 13 cognitive tests but below the normal in selected tests of verbal attainment, attention and deductive thinking. Perfusion of anterior cortical and subcortical regions of the dominant hemisphere was directly correlated with the number of correctly performed neuropsychologic tests. In conclusion, anterior cerebral hypoperfusion and selected neuropsychological dysfunctions characterized hypoxemic COPD patients and could herald frontal-type cognitive decline with the worsening of the hypoxemia.