In this proposal we request to observe a sample of high latitude clouds for which the observed the 12CO versus I100 (as determined from IRAS) correlation dramatically deviate from the general pattern observed in our galaxy. The clouds in our target list can be classified as (i) IR deficient clouds, (ii) CO deficient clouds (iii) clouds with wide CO lines, (iii) clouds with high 25 and 60 micron IRAS fluxes. For each of the classes we have selected a best representative. We want to obtain deep infrared maps at different FIR wavelengths with ISOPHOT to determine the distribution and abundance of the dust grains as well as deep [OI] 63 micron and [CII] 158 micron measurements with LWS to quantify the role of the UV radiation field and/or the neutral carbon content. These observations should provide constraints to the explanations suggested for these anomalies.