This paper reports the observation of exceptionally narrow resonant responses in transmission and reflection of planar metamaterials achieved through introducing asymmetry into its structural elements. The appearance of narrow resonances is attributed to the excitation of otherwise forbidden anti-symmetric modes, which are weakly coupled to free-space ("dark modes"). The metamaterials used in the experiments consisted of identical sub-wavelength metallic "inclusions" structured in the form of asymmetrically split rings (ASR), arranged in a periodic array on a thin dielectric substrate. The results showed that the transmission and reflection properties strongly depend on the polarization state of the incident electromagnetic waves. For certain polarizations, the ASR-structures exhibited sharp resonances with high quality factors (Q), which are essential for efficient metamaterial performance. The high-Q resonances were achieved by introducing small asymmetries in the shape of the structural elements, enabling the excitation of dark modes. Theoretical modeling using the method of moments confirmed the experimental results, showing good agreement between theory and experiment. The origin of the strong and narrow spectral responses was traced to dark modes, which are weakly coupled to free-space. The introduction of asymmetry in the split-ring structure allowed for the creation of a very narrow pass-band within its transmission stop-band. The results demonstrate that asymmetrically split ring metamaterials can achieve high-Q resonances with significantly higher quality factors compared to conventional metamaterials. This work highlights the potential of dark-mode resonances in planar metamaterials with broken structural symmetry for applications in the optical spectrum where losses are significant.This paper reports the observation of exceptionally narrow resonant responses in transmission and reflection of planar metamaterials achieved through introducing asymmetry into its structural elements. The appearance of narrow resonances is attributed to the excitation of otherwise forbidden anti-symmetric modes, which are weakly coupled to free-space ("dark modes"). The metamaterials used in the experiments consisted of identical sub-wavelength metallic "inclusions" structured in the form of asymmetrically split rings (ASR), arranged in a periodic array on a thin dielectric substrate. The results showed that the transmission and reflection properties strongly depend on the polarization state of the incident electromagnetic waves. For certain polarizations, the ASR-structures exhibited sharp resonances with high quality factors (Q), which are essential for efficient metamaterial performance. The high-Q resonances were achieved by introducing small asymmetries in the shape of the structural elements, enabling the excitation of dark modes. Theoretical modeling using the method of moments confirmed the experimental results, showing good agreement between theory and experiment. The origin of the strong and narrow spectral responses was traced to dark modes, which are weakly coupled to free-space. The introduction of asymmetry in the split-ring structure allowed for the creation of a very narrow pass-band within its transmission stop-band. The results demonstrate that asymmetrically split ring metamaterials can achieve high-Q resonances with significantly higher quality factors compared to conventional metamaterials. This work highlights the potential of dark-mode resonances in planar metamaterials with broken structural symmetry for applications in the optical spectrum where losses are significant.