This study compares near-infrared spectroscopy (NIRS) and functional magnetic resonance imaging (fMRI) across multiple cognitive tasks. NIRS measures changes in oxygenated and deoxygenated hemoglobin, offering finer temporal resolution and ease of use, but has inferior spatial resolution and lower signal-to-noise ratio (SNR) compared to fMRI. While fMRI is the gold standard for brain imaging, NIRS is more convenient and less expensive. The study used simultaneous NIRS and fMRI to examine correlations between signals in both temporal and spatial domains. NIRS signals showed weaker SNR but were often highly correlated with fMRI measurements. Spatial correlation was strongest when the photon path between NIRS emitter and detector formed an ellipse. The scalp-brain distance and SNR influenced NIRS/fMRI correlations. NIRS signals were more correlated with fMRI in tasks with higher SNR and shorter scalp-brain distances. The study found that NIRS can be a suitable alternative to fMRI for cognitive tasks, but care must be taken to ensure adequate spatial resolution and account for lower SNR, especially in regions farther from the scalp. The results suggest that NIRS and fMRI signals are strongly correlated in cognitive tasks, but the correlation varies depending on task type, SNR, and scalp-brain distance. The study also found that the optimal ROI shape for NIRS-fMRI correlation is an elliptical ring. The findings highlight the potential of NIRS as a complementary tool to fMRI in cognitive neuroscience research.This study compares near-infrared spectroscopy (NIRS) and functional magnetic resonance imaging (fMRI) across multiple cognitive tasks. NIRS measures changes in oxygenated and deoxygenated hemoglobin, offering finer temporal resolution and ease of use, but has inferior spatial resolution and lower signal-to-noise ratio (SNR) compared to fMRI. While fMRI is the gold standard for brain imaging, NIRS is more convenient and less expensive. The study used simultaneous NIRS and fMRI to examine correlations between signals in both temporal and spatial domains. NIRS signals showed weaker SNR but were often highly correlated with fMRI measurements. Spatial correlation was strongest when the photon path between NIRS emitter and detector formed an ellipse. The scalp-brain distance and SNR influenced NIRS/fMRI correlations. NIRS signals were more correlated with fMRI in tasks with higher SNR and shorter scalp-brain distances. The study found that NIRS can be a suitable alternative to fMRI for cognitive tasks, but care must be taken to ensure adequate spatial resolution and account for lower SNR, especially in regions farther from the scalp. The results suggest that NIRS and fMRI signals are strongly correlated in cognitive tasks, but the correlation varies depending on task type, SNR, and scalp-brain distance. The study also found that the optimal ROI shape for NIRS-fMRI correlation is an elliptical ring. The findings highlight the potential of NIRS as a complementary tool to fMRI in cognitive neuroscience research.