We present a novel, hybrid ion trap/time-of-flight mass spectrometer that is based on a planar multipole design. Compared with Paul trap/time-of-flight instruments, this design possesses the principal advantages of higher injection efficiency and more homogeneous extraction fields. We demonstrate the viability of the concept and describe the characterization of a first prototype. Ions can be injected into the trap with little mass discrimination and stored for several minutes. A resolution of over 1300 is achieved in reflectron mode, and the influence of the RF amplitude and pressure on the resolution is analyzed. We suggest several applications in which this new instrument could offer advantages over existing technology.