Axial collision induced dissociation (CID) and high-pressure resonance CID were implemented and compared with normal low-pressure resonance CID in a miniature ion trap mass spectrometer to obtain more complete fragmentation spectra. Axial CID was realized simply by applying a potential to the discontinuous atmospheric pressure interface (DAPI) capillary without performing parent ion isolation before dissociation. High-pressure resonance CID employed a double-introduction pulse scan function, by means of which precursor ions isolated at low-pressure (<10⁻³ torr) were dissociated at high-pressure (0.1 torr-1 torr) with higher excitation energy, so that tandem MS of isolated precursor ions was achieved and extensive fragmentation was obtained. A simple peptide (Leu-enkephalin) and dye molecule (rhodamine B) ionized by ESI were used to investigate both methods and compare them with normal low-pressure resonance CID.