Polydimethylsiloxane (PDMS) has a strong, characteristic ToF-SIMS spectrum, and microcontact printing with PDMS stamps usually leads to "undesired" PDMS oligomer transfer to stamped substrates. Here we take advantage of this phenomenon. That is, we have observed that PDMS oligomer transfer from flat PDMS stamps takes place readily to hydrophilic surfaces, but is limited or absent on hydrophobic surface. This effect allows ToF-SIMS of PDMS oligomer transfer on surfaces to be an effective probe for hydrophilic and hydrophobic surfaces, especially those patterned with micron-sized features. For example, microlens array patterned substrates containing hydrophilic spots on a hydrophobic background showed selective PDMS transfer to the spots, but not the backgrounds, allowing ready identification of the more hydrophilic spots. This approach can also be used to probe the wetting behavior of single materials, such as surfaces covered with thin films of C60 and trihexadecyloxybenzaldehyde (THOB), where PDMS transfer is observed by ToF-SIMS on the former material, but not on the latter, presumably because of its more hydrophobic alkyl chains.