Electrohelicity appears as helical molecular orbitals (MOs) in allene and spiropentadiene when their symmetry is reduced from D 2d to D 2 (or C 2 ). In allene both the degenerate sets of highest occupied MOs (HOMOs) and the lowest unoccupied MOs (LUMOs) are helical (Figure only the HOMOs are helical while the non-degenerate LUMO and LUMO+1 are delocalized due to spiroconjugation (Figure right). These helical frontier MOs are present in several types of linear carbyne-like and spiroconjugated molecules due to the Möbius topology of the π-system. We recently demonstrated a correlation exists between the chiroptical response and the splitting of the near-degenerate helical MO pairs in substituted allenes and longer odd-carbon cumulenes. In this article, we examine the underlying connection between electrohelicity and optical activity in molecules where helical frontier MOs appear. We treat four types of molecules that exhibit electrohelicity: Subsection 3.1 covers allene, 3.2 evencarbon cumulenes, 3.3 polyynes, and 3.4 spiropentadiene. Each of these subsections can in principle be read independently of each other. First, we show that the optical activity of chiral allenes is driven by the helicity of the frontier MOs, and we demonstrate strategies for optimizing the chiroptical response. Then we examine linear and spiroconjugated systems where the helical frontier MOs may not contribute directly to the optical activity. Finally, we discuss the potential implications of these results going forward in the conclusions section.