Two different types of Y-films (a Y-film from Z-type deposition and a Y-film from Y-type deposition) have been observed during the Langmuir-Blodgett (LB) film deposition of metal diynoates, but their structural characterisation has not received much attention. In the present work, a study of LB film deposition of cadmium 10,12-pentacosadiynoate, for evaluating the effects of monolayer aging and concentration of spreading solution, has been carried out and three different types of Y-films of cadmium 10,12-pentacosadiynoate have been obtained. Structural characterisation and study of the topochemical polymerisation of different types of films show remarkably large differences in their bilayer spacing and diacetylene polymerisation behaviour. This study shows that Y-films obtained by overturning in the Z-type buildup process are structurally quite different from the Y-films obtained from the Y-type build-up process.