Comparison of the CO-dark and CO-bright maps. Upper panel: full-sky CO-dark map, showing sightlines with cm^-2 but devoid of CO (W_CO < 1 Kkm s^-1). Bottom panel: CO-bright map, corresponding to cm^-2 and W_CO > 1 K km s^-1. The CO-dark H₂ spans an area approximately equal to 17% of the total sky. This is a factor of 2 larger than that of the CO-bright H₂, and extends up to high Galactic Latitude. On the other hand, CO-bright H₂ is mostly concentrated toward the Galactic plane. Moving away from the Galactic plane, we observe that H₂ transitions from CO-bright to CO-dark form at |b| ≈ 5 deg. Although we still observe a few CO-bright H₂ regions at higher latitudes above the Galactic plane, most of the molecular gas is in the CO-dark form there.