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<p>Trifluoromethane (CHF<span class="inline-formula">₃</span>, HFC-23), one of the most potent greenhouse gases among hydrofluorocarbons (HFCs), is mainly emitted to the atmosphere as a by-product in the production of the ozone-depleting legacy refrigerant and chemical feedstock chlorodifluoromethane (CHClF<span class="inline-formula">₂</span>, HCFC-22). A recent study on atmospheric observation-based global HFC-23 emissions (top-down estimates) showed significant discrepancies over 2014–2017 between the increase in the observation-derived emissions and the 87 % emission reduction expected from capture and destruction processes of HFC-23 at HCFC-22 production facilities implemented by national phase-out plans (bottom-up emission estimates) (Stanley et al., 2020). However, the actual regions responsible for the increased emissions were not identified. Here, we estimate the regional top-down emissions of HFC-23 for eastern Asia based on in situ measurements at Gosan, South Korea, and show that the HFC-23 emissions from eastern China have increased from <span class="inline-formula">5.0±0.4</span> Gg yr<span class="inline-formula">⁻¹</span> in 2008 to <span class="inline-formula">9.5±1.0</span> Gg yr<span class="inline-formula">⁻¹</span> in 2019. The continuous rise since 2015 was contrary to the large emissions reduction reported under the Chinese hydrochlorofluorocarbons production phase-out management plan (HPPMP). The cumulative difference between top-down and bottom-up estimates for 2015–2019 in eastern China was <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mn mathvariant="normal">23.7</mn><mo>±</mo><mn mathvariant="normal">3.6</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="60pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="5c3605c4168f85d728d34f3f1930e4b0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-9401-2023-ie00001.svg" width="60pt" height="10pt" src="acp-23-9401-2023-ie00001.png"/></svg:svg></span></span> Gg, which accounts for <span class="inline-formula">47±11</span> % of the global mismatch. Our analysis based on HCFC-22 production information suggests the HFC-23 emissions rise in eastern China is more likely associated with known HCFC-22 production facilities rather than the existence of unreported, unknown HCFC-22 production, and thus observed discrepancies between top-down and bottom-up emissions could be attributed to unsuccessful factory-level HFC-23 abatement and inaccurate quantification of emission reductions.</p>