Resonance-enhanced multiphoton ionization combined with electronic ground state depletion spectroscopy of jet-cooled 2-methylallyl (C 4H 7) radicals provides vibronic spectra of the 3 s and 3 p Rydberg states. Analysis of the vibronic structure following one-photon and two-photon excitation of rovibronically cold 2-methylallyl radicals and its isotopologues C 4H 4D 3 and C 4D 7 reveals transitions to more than 30 vibrational levels in the 3 s Rydberg state that are identified and reassigned on the basis of predictions from ab initio calculations and results from pulsed-field-ionization zero-kinetic-energy photoelectron spectra obtained with resonant multiphoton excitation via selected intermediate states. Depletion spectroscopy reveals transitions to short-lived 3 p Rydberg states that have a large oscillator strength.