As one of the most toxic heavy metals, cadmium pollution in soil has spawned much attention concerning environmental factors affecting its bioavailability to plants and development of agricultural practices for reducing its uptake by staple crops. Recently, it has been established that mobile colloidal particles in soil can act as carriers for strongly sorbing chemicals, and thus facilitate the vertical transport of contaminants, such as heavy metals. This colloid-facilitated transport of cadmium can be of particular concern in converted “ex-paddy” fields with shrinkage cracks in the subsurface layer, where the vertical transport of colloidal particles through macropores and cracks has been found remarkable. Given the importance of colloid-facilitated and dissolved vertical transport of cadmium in soils, repeated batch extraction experiments were conducted to examine the effects of solution pH and ionic composition and concentrations on cadmium retention by different particle-size fractions of converted “ex-paddy” soils. The soil pH was changed through addition of calcium hydroxide, for liming is often practiced as a measure to reduce the bioavailability of heavy metals in soils, and may affect both the cadmium retention and dispersion of soil aggregates. Two contrasting moist soils, Takada clayey soil and Chiba sandy soil, were used in the batch experiments. The relative importance of soil particles in different size fractions in colloid-facilitated cadmium transport was estimated. These data form a basis for elucidating relative contribution of the dissolved and colloid-associated cadmium to the downward flux from the contaminated soil layer under different conditions.