COVID-19 lockdowns worldwide in 2020 have resulted in dramatic reductions of emissions from closed factories, reduced vehicular road traffic, shut down of airline flights and other activities using fossil fuels. In most countries with increasing numbers of coronavirus infections, billions of people have been told to stay at home. In China, authorities placed almost half a billion people under lockdown for more than 60 days, the equivalent of nearly 7% of the world’s population. Many other countries have since taken similar measures, initially in hard-hit Italy and Spain, and more recently in the United States and India, UK, Japan, Germany and other developed countries. While the corronavirus pandemic lockdowns for more than 3 months have inflicted substantial economic, social and employment damage, they have also been associated with significant reductions in air pollution and greenhouse gas emissions. Closing factories, dramatically reducing vehicular traffic, and lower consumption of fossil fuels for energy generation made a great difference in atmospheric emissions. The COVID-19 pandemic caused also serious problems to most health systems all over the world and postponment numerous other critical health care functions to millions of patients and old age people. The total result of all these lockdown measures was a dramatic improvement of air quality levels in the world’s major cities in March and April 2020. Air quality improved largely because of a reduction in factory and road traffic emissions of carbon dioxide (CO2), nitrogen oxides (NOx) and photochemical ozone (O3) formation. But the most dramatic reduction in urban areas was in emissions of particulate matter (PM, PM10, PM2.5) because of reduced vehicular exhaust superfine particles. Data of air pollutants were collected for NO2 and O3 from the TROPOspheric Monitoring 259 Instrument on‐board the Copernicus Sentinel‐5 Precursor satellites (a fleet of dedicated EU satellites, designed to deliver the wealth of data and imagery).The European Environment Agency (EEA) collected data of hourly measurements on the ground at about 3,000 monitoring stations actoss most European countries in March and April 2020 under lockdown measures. Data confirmed large decreases in air pollutant concentrations. Very interesting pictures from major cities in China, South Korea, European countries (Milan, Paris, Warsaw, etc) and american cities proved the reductions This review contains some very interesting photos of major cities from before and after the pandemic months and levels of reduction in air pollutants for various countries copmpared to similar months in 2019.