Detection of ?- and ?-particles is of paramount importance in a wide range of applications. Current particle detectors are all macroscopic and have limited time resolution. We demonstrate a nanoscale particle detector with a small detection volume, high detection efficiency, short dead times and low dark count levels. We measure ?- and ?-particle detection efficiencies close to unity using different sources and also demonstrate blindness towards ?-rays. Our nanoscale detector offers particle detection measurements with unprecendented spatial resolution.