We present aperture synthesis CO maps of two 2'-fields of M51. These maps, in contrast to previous interferometer maps, do not have any missing flux. They show directly that most of the CO emission arise from broad spiral arms, whereas previously it was assumed that the missing CO flux (≥ 65% of the total flux) is uniformly distributed. Inferences involving extended CO emission and widths of the CO spiral arms based on interferometer maps with missing flux may need to be reviewed. The “missing short spacings” problem is also discussed.