"What Were We Thinking Of" is a song recorded by American singer Barbra Streisand for her 25th studio album, Till I Loved You (1988).

It features guest vocals from the singer's then-boyfriend Don Johnson, who had previously collaborated with Streisand on her 1988 single "Till I Loved You".

The singer remarked that she enjoyed duetting with him because he is "very musical and has a unique sounding voice"; she was also interested in their collaborations due to the fact that he was able "act" out the lyrics while singing.

[4] Because of the success they had found while creating the aforementioned track, it was decided that Johnson would also lend his voice for background vocals on "What Were We Thinking Of".

Paul Grein, a writer for the Los Angeles Times, considered the song and "Some Good Things Never Last" as the two best cuts on side two of the parent album.

[16] The single did not enter the Billboard Hot 100 in the United States, but did reach the same publication's Adult Contemporary chart.