Normal, neutral, and inverse‐type Diels–Alder reactions can be observed in [4+2] cycloadditions of thio‐ and selenocarbonyl compounds 1–9 with various cyclic and aryl‐, methyl‐ or methoxy‐substituted open‐chain 1,3‐butadienes. Extensive kinetic studies prove the highly dienophilic activity of the CS and CSe double bond. Studies of the solvent and temperature dependence of the reaction rate indicate a concerted mechanism.