We have obtained EUV spectra between 90 and 255 8 of the comets C/2002 T7 (LINEAR), C/2001 Q4 (NEAT), and C/2004 Q2 (Machholz) near their perihelion passages in 2004 with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS). We obtained contemporaneous data on NEAT with the Chandra ACIS instrument, marking the firstsimultaneousEUVandX-rayspectralobservationsofacomet.ThetotalCHIPS/EUVobservingtimeswere337ks for NEAT, 234 ks for LINEAR, and 483 ks for Machholz, and for both CHIPS and Chandra we calculate we have capturedall the comet flux in the instrumentfield of view. We set upper limits on solar wind charge-exchange emission lines of O, C, N, Ne, and Fe occurring in the spectral bandpass of CHIPS. The spectrum of NEAT obtained with ChandracanbereproducedbymodelingemissionlinesofC,N,O,Mg,Fe,Si,S,andNesolarwindions.Themeasured X-rayemission-lineintensitiesareconsistentwithourpredictionsfromasolarwindcharge-exchangemodel.Themodel predictions for the EUVemission-line intensities are determined from the intensity ratios of the cascading X-ray and EUVphotonsarisinginthecharge-exchangeprocesses.Theyarecompatiblewiththemeasuredlimitsontheintensities of the EUV lines. For NEAT, we measured a total X-ray flux of 3:7 ; 10 � 12 ergs cm � 2 s � 1 and derive from model predictions a total EUV flux of 1:5 ; 10 � 12 ergs cm � 2 s� 1. The CHIPS observations occurred predominantly while the satellite was on the dayside of Earth. For much of the observing time, CHIPS performed observations at smaller solar angles than it was designed for, and EUVemission from the Sun scattered into the instrument limited the sensitivity of the EUV measurements. Subject headingg comets: general — comets: individual (C/2002 T7 (LINEAR), C/2001 Q4 (NEAT), C/2004 Q2 (Machholz)) — ultraviolet: solar system