Others view them as indecisive in their actions, self-absorbed, absent-minded and detached from their surroundings. Excessive daydreaming is often present. In cases with severe defects in the capacity to form social relationships, dating and marriage may not be possible. ICD-10 criteria
The Classification of Mental and Behavioural Disorders of ICD-10 lists SzPD under (F60.1).The general criteria of personality disorder (F60) should be met first. In addition, at least four of the following criteria must be present:

Few, if any, activities provide pleasure. Displays emotional coldness, detachment, or flattened affectivity. Limited capacity to express warm, tender feelings for others as well as anger. Appears indifferent to either praise or criticism from others. Little interest in having sexual experiences with another person (taking into account age). Almost always chooses solitary activities. Excessive preoccupation with fantasy and introspection. Neither desires, nor has, any close friends or confiding relationships (or only one). Marked insensitivity to prevailing social norms and conventions; if these are not followed, this is unintentional. Guntrip criteria
Ralph Klein, Clinical Director of the Masterson Institute, delineates the following nine characteristics of the schizoid personality as described by Harry Guntrip:: 13–23 
Introversion
Withdrawnness
Narcissism
Self-sufficiency
A sense of superiority
Loss of affect
Loneliness
Depersonalization
RegressionThe description of Guntrips nine characteristics should clarify some differences between the traditional DSM portrait of SzPD and the traditional informed object relations view. All nine characteristics are consistent. Most, if not all, must be present to diagnose a schizoid disorder. Millons subtypes
Theodore Millon restricted the term "schizoid" to those personalities who lack the capacity to form social relationships.
It has also been argued due to the poor consistency and efficiency of diagnosis due to overlapping traits that SzPD should be removed altogether from the DSM.A 2012 article suggested that two different disorders may better represent SzPD: one affect-constricted disorder (belonging to schizotypal PD) and a seclusive disorder (belonging to avoidant PD). They called for the replacement of the SzPD category from future editions of the DSM by a dimensional model which would allow for the description of schizoid traits on an individual basis.Some critics such as Nancy McWilliams of Rutgers University and Parpottas Panagiotis of European University Cyprus argue that the definition of SzPD is flawed due to cultural bias and that it does not constitute a mental disorder but simply an avoidant attachment style requiring more distant emotional proximity. If that is true, then many of the more problematic reactions these individuals show in social situations may be partly accounted for by the judgements commonly imposed on people with this style. However, impairment is mandatory for any behaviour to be diagnosed as a personality disorder. SzPD seems to satisfy this criterion because it is linked to negative outcomes. These include a significantly compromised quality of life, reduced overall functioning even after 15 years and one of the lowest levels of "life success" of all personality disorders (measured as "status, wealth and successful relationships"). However, determination of what qualify as "impairments" or as "negative outcomes" is itself potentially subject to cultural bias.