The genome of coronaviruses, including the SARS-CoV-2, which causes the human pandemic COVID-19, encodes for two proteases, a papain like (PL) and the so-called Main protease (Mpro), also named 3CLpro or non-structural protein 5 (NSP5). Mpro is activated by autoproteolysis, and true to its name, is the main protease responsible for cutting the viral polyprotein into functional viral proteins. Aside from this function, it has been described that 3CL proteases are also capable to process host proteins, including those involved in the host innate immune response. We performed a LC-MS based N-terminomics analysis to identify in vitro substrates of three different recombinantly expressed coronavirus main proteases (SARS-CoV, SARS-CoV-2, hCoV-NL63) using lung cell lysates as substrate pools.