Terminal mineralization of organic carbon (C) in northern peat soils usually produces more carbon dioxide (CO₂) than methane (CH₄), but the maintenance of microbial CO₂ production is unclear. Carbon dioxide production relies on oxygen (O₂) or alternative (to O₂) electron acceptors (NO₃⁻, Fe(III), SO₄²⁻). We examined rates of CO₂ production and CH₄ production in peat soils from two ombrotrophic bogs and two minerotrophic fens incubated in vitro with and without added glucose (an electron donor) and added electron acceptors. Soil interstitial water had dissolved NO₃⁻ (2–17 µmol L⁻¹) in three sites, and SO₄²⁻ (2–20 µmol L⁻¹) and Fe(III) (0.02–0.8 µmol L⁻¹) in all four sites. Peat soils incubated in vitro without added glucose or electron acceptors had rates of CH₄ production between 0.2 and 1.5 µmol g⁻¹ day⁻¹ and rates of CO₂ production between 8 and 17 µmol g⁻¹ day⁻¹. Added glucose increased CO₂ production in all of the peat soils, although adding an electron acceptor with glucose had no additional impact in the bogs. Nitrate plus glucose had the largest increase in CO₂ production in both fens, and SO₄²⁻ plus glucose enhanced CO₂ production in one fen. Added glucose alone or with O₂ or Fe increased CH₄ production in peat soil from the two bogs, whereas glucose plus SO₄²⁻ or NO₃⁻ inhibited CH₄ production. Glucose plus an electron acceptor inhibited CH₄ production in the forest fen but enhanced CH₄ production in sedge fen. Terminal electron acceptors did not universally divert C and electron flow away from CH₄ production and towards CO₂ production in these peat soils, and thus maintenance of CO₂ production is still uncertain, with no single explanation likely.