An analysis of excess mortality in Switzerland in 2020 before the 2nd wave of COVID-19 is proposed by comparing the number of deaths observed in 2020 with those of the last five years, while taking into account population growth. Three periods are identified : before, during and after the 1st wave of COVID-19. Over all these periods, a sub-mortality of -3.3 % is obtained at the national level. However, if we restrict the analysis to the period during the first wave and to the cantons most affected by the virus, we obtain an important excess mortality, up to more than 80 % in Ticino, showing that these calculations depend crucially on when, where and for whom the deaths are counted. Such an analysis will have to be repeated once the 2nd wave is over in order to estimate the overall impact of the epidemic on excess mortality in Switzerland.