With the growing older adult population, neurodegenerative diseases common in old age such as mild cognitive impairment (MCI) or Parkinson’s disease (PD) are becoming increasingly germane areas of research. Pharmacological treatments have thus far been unsuccessful in treating cognitive decline associated with these neurodegenerative disorders. Alternative interventions, such as cognitive training programs, have shown promise. The current dissertation contains three papers examining cognitive interventions in neurodegenerative diseases. The first paper examined the longitudinal effects of cognitive speed of processing training (SPT) among those with PD. Results showed that training gains seen at initial post-test were maintained three months later. The second paper examined the effects of SPT among those with psychometrically-defined MCI and found small to medium effect sizes for improvements in everyday functional performance among those trained. The third paper examined the effects of auditory cognitive training among cognitively healthy older adults and those with psychometrically-defined MCI and found that effects may differ between those with and with MCI. Overall, these papers show that training effects can be maintained longitudinally and may potentially transfer to everyday functioning in those with neurodegenerative diseases. However, not all cognitive training programs show benefits in all areas, and individuals with differing cognitive statuses may benefit differentially from cognitive training. Future research should further explore the longitudinal effects of these training programs as well as the possibility of transfer to untrained abilities.