The developing world will largely determine the trajectory of future global CO2 emissions. An accurate projection of CO2 emissions from the developing world and a good understanding of possible timelines and pathways to reach their peaks are of great significance to combat global climate change. This issue has recently attracted increasing attention; however, it is far from solved. China and India are the two largest developing countries and have a decisive influence on CO2 emissions growth across the developing world. This article critically reviews the current literature regarding CO2 emissions projections of the developing world, particularly of China and India, with an aim to summarize recent study progresses and enlighten future studies. It is generally agreed that China will peak its CO2 emissions by 2030 and has an excellent chance of reaching an earlier peak during 2020-2030. By contrast, India is very likely to undergo sustained emissions growths for decades. The constraints of keeping global warming below 2 degrees C may enable India to peak CO2 emissions by 2040; however, the associated costs will be too high to pay. Across the developing world, the timeline to peak CO2 emission remains difficult to determine; however, a rapid transition of major developing countries towards low-carbon sustainable development is essential for reaching such a peak. Four topics urgently require further study in the future: improvements in study methodology and data, key country groups and fields to peak CO2 emissions, the peak morphology and post-peak CO2 emissions in China, and a more in-depth understanding of the timeline and pathway to peak CO2 emissions in India.