Placing transparent links in InDesign

I created some tiff files with transparent edges in Photoshop. Then I placed them in InDesign CS4. Then. I put some colored shape behind the Tiff Images. However, the placed link edges look white instead of transparent. What should I do in order to work with half transparent images placed inside the InDesign. Do I have to convert them to "psd" files if the TIFF doesn't work that way?

Thanks