Structural refinements of the new compounds Bi2Sr3_ xYxCu208 + y in the range of x that gives insulating rather than superconducting behaviour (x~ 0.6 and 1.0) have been obtained from single crystal X-ray and neutron powder diffraction data. Results indicate oxygen nonstoichiometry and suggest condensation into pairs or chains of the Bi-O atoms along the a axis in the Bi-O double layers. Chain-like formation can be found between the copper-oxygen sheets of all the orthorhombic superconductors including La2CuO4. XANES studies show that the oxidation state of copper (Cu 2+ ) is not affected by yttrium substitution for strontium. The mechanism of charge compensation appears to involve the insertion of oxygen, over the ideal Oa composition, in (rather than between) the Bi-O sheets. These materials are orthorhombic and the lattice parameters for the subcell of the x~0.6 material are a=5.467(3), b=5.4407(6), c=30.434(5) A, space group Amaa, Z=4. The x~l.0 phase has a=5.467(2), b = 5.426 ( 1 ), and c = 30.183 (8) A. The structure is essentially the same as that of superconducting Bi2Sr 3_xCaxcu2Os+y. Electron diffraction patterns for the yttrium-containing phases show an incommensurate supedattice along the a axis as seen in the calcium analog. This is due to atomic displacements that are modulated along a with amplitudes in the c direction.