Four manganese carbonyl complexes: CpMn(CO)3 (1) and its phenylvinylidene derivatives Cp(CO)2Mn=C=CHPh (2), [Cp(CO)2Mn]2(μ-C=CHPh) (3), and Cp(CO)2Mn=C=C(Ph)–C(Ph)=C=Mn(CO)2Cp (4) have been studied by X-ray powder diffraction and their unit cell parameters are reported. The monoclinic cell parameters found for complex (1) are a=12.0479(7) Å, b=7.0614(5) Å, c=10.9172(6) Å, β=117.626(2)°, Z=4, space group P2(1)/a (No. 14). The orthorhombic cells parameters for complex (2) are a=10.5240(12) Å, b=33.1105(48) Å, c=7.5007(9) Å, Z=8, space group PCCN (No. 56); for complex (3) are a=15.3545(17) Å, b=15.3966(18) Å, c=8.0033(7) Å, Z=4, space group P21212121 (No. 19). The parameters found for complexes (1–3) are in good agreement with those obtained from single crystal X-ray diffractometry. The single crystal structure of complex (4) has not been studied. The orthorhombic cell parameters for complex (4) found by X-ray powder diffraction method are a=10.0986(9) Å, b=33.2937(27) Å, c=7.4139(5) Å, Z=4, space group P21 (No. 4).