A device for combined respiratory gas analysis and lung function test includes a gas quantity measuring device, a gas analysis device, and a multi-way valve configured for placement at least between a first valve path combination and a second valve path combination. A first gas path between the gas quantity measuring device and a second combined inlet/outlet opening is established while by-passing the gas analysis device with the first valve path combination of the multi-way valve, and a second gas path is established between a first combined inlet/outlet opening, the gas analysis device, the gas quantity measuring device, and the second combined inlet/outlet opening with the second valve path combination of the multi-way valve.