Abstract Introduction Neurocognitive impairments are common in individuals with insomnia and sleep apnea separately, however, the evidence for impairment in comorbid insomnia and sleep apnea (COMISA) is much less clear. We aim to determine a neurocognitive profile for individuals with COMISA, and evaluate the benefits of treatment on neurocognitive performance. Methods Participants with COMISA (n=45; 51.1% female; mean age=52.07±13.29) were from a two-phase, 3-arm randomized clinical trial combining Cognitive Behavioral Therapy for insomnia (CBT-I) with Continuous Positive Airway Pressure (CPAP) administered sequentially or concurrently compared to CPAP alone. The unique groups from this factorial design were used to establish baseline impairment and the effects of treatment on neurocognitive functioning. Results Individuals with COMISA had a slower reaction time (365.66±157.39) and more lapses (9.70±16.16) on the Psychomotor Vigilance Task than has been reported in the literature for insomnia and OSA separately. Our COMISA participants had mean scores indicating mild impairment for their age, based on normative data, on digit span (9.71±2.47 forward; 3.95±2.63 backward), verbal paired associates (27.71±11.54 immediate; 8.69±3.16 delayed; 37.17±2.97 recognition), Digit Symbol Substitution (68.83±12.33) and the Stroop (35.46±7.26 color/word; -3.19±7.5 interference). The only significant treatment outcome was in the acute effect after CBT-I on digit span forward (1.7 fewer digits remembered after CBT-I vs. 0.2 fewer after no treatment, t(32)=-2.1, p=0.047). This effect was no longer significant after controlling for multiple comparisons. Conclusion This is the first study to report baseline neurocognitive impairments and effects after treatment for individuals with COMISA. Baseline impairments appear to be more significant than reported in the literature for conditions individually and published norms. Results indicate a worsening in neurocognitive functioning after CBT-I, however the numbers within the groups are small, and this effect disappears after controlling for multiple comparisons. Future studies are necessary to provide a conclusive answer regarding the effects of treatment on neurocognition. Support NIH/NHLBI (R01 HL114529-03S1) Ong 1/7/2015 - 6/30/2017 Project Title: Multidisciplinary Treatment for Obstructive Sleep Apnea and Insomnia - Research Supplement to Promote Diversity in Health-Related Research