AbstractTreatment of [η6‐(bicyclo[4.2.0]octa‐1,3–5 triene)]tricarbonylchromium(0) (2) with BuLi or lithium 2,2,6,6‐tetramethylpiperidinide (TMPLi) gives rise to a highly regioselective deprotonation at C(2). Subsequent reaction with electrophiles (6 examples) gives [η6‐(2‐R‐bicyclo[4.2.0]octa‐1,3,5‐triene)]tricarbonylchromiurn complexes 3 and 5–9 in moderate (RI, 50%; RCHO, 67%) to good (RMe, D, SiMe3, CO2Me, > 80%) yield (Scheme 1). Analogous reactions with tricarbonyl (η6‐indane)chromium (10) give mixtures of complexes substituted at C(4) and C(5) (Scheme 2). In 10, deprotonation β to the ring junction is strongly favoured with the bulky base TMPLi. Double lithiation/electrophile additions to 2 give access to [η6‐(2‐R′‐5‐R″‐bicyclo[4.2.0]octa‐1,3,5‐triene)]tri‐carbonylchromium complexes (e.g. 13 (R′R″Me3Si) and 14 (R′Me3Si, R″CHO)) as single products. The Cr(CO)3 group can be easily removed by oxidation (I2, Ce(IV), O2/light; 2 examples each) to give the free arenes. Base‐catalyzed (CsF, DMF/D2O) deuterodesilylation of 13 yields the [(2,5‐2H2)bicyclo[4.2.0]octa‐1,3,5‐triene]chromium complex 15, and treatment of 2,5‐bis(trimethylsilyl) compound 16 with CF3COOD gives the 2,4‐dideuterated 17. Compound 16 is also accessible more directly via reductive silylation/oxidation of bicyclo[4.2.0]octa‐1,3,5‐triene (1). Stereoselective base‐catalyzed (t‐BuOK.) H/D exchange of the benzylic H‐atoms. opposite to the Cr(CO)3 moiety in 2 takes place rapidly in (D6)DMSO, but benzylic functionalization via this route remains elusive.