According to the 2001 Swiss Census poll, 4.3% identified as having no religion.
Regarding personal belief, the 2005 Eurobarometer poll found that 48% of Swiss citizens expressed belief "that there is a God", 39% expressed belief in "some sort of spirit or life force", while 9% answered that they did not believe that "there is any sort of spirit, God, or life force". Religion has declined in Switzerland.
References
Irreligion in Switzerland Wikipedia(Text) CC BY-SA